Steam system

Abstract

A steam system configured to heat water, comprising: a heat exchanger configured to receive steam and water, configured to heat water with steam; a steam supply line configured to be connected to a steam source to supply steam to the heat exchanger; a condensate line configured to receive condensate from condensed steam from the heat exchanger and to guide the condensate out of the heat exchanger; a feed water line configured to supply water to the heat exchanger; a discharge line configured to receive heated water from the heat exchanger and to guide the heated water out of the heat exchanger; a steam valve positioned on the steam supply line and configured to control the flow of steam through the steam supply line; and a steam valve positioned on the condensate line and passing through the condensate line. A steam system comprising: a condensate valve configured to control the flow of condensate; a first sensor located downstream of the steam valve and upstream of the condensate valve, configured to output a pressure signal indicating the pressure between the steam valve and the condensate valve in the steam system; and / or a second sensor located at the condensate outlet, configured to output a condensate temperature signal indicating the temperature of the condensate between the heat exchanger and the condensate valve in the condensate line; a third sensor located on the discharge line, configured to output a water temperature signal indicating the temperature of the heated water passing through the discharge line; and a controller configured to control the opening and closing of the steam valve and the condensate valve based on the water temperature signal and at least one of the pressure signal and the condensate temperature signal.

Description

Technical Field

[0001] The present invention relates to a steam system configured to heat water, a method of controlling such a steam system, and a method of designing such a steam system.

Background Art

[0002] Steam systems are commonly used to heat water and are used in domestic hot water systems and the like. Such steam systems can be controlled in various ways to control the water temperature.

Summary of the Invention

Means for Solving the Problems

[0003] According to a first aspect, a steam system configured to heat water, a heat exchanger configured to receive steam and water, the heat exchanger being configured to heat the water with the steam, a steam supply line configured to be connected to a steam source to supply steam to the heat exchanger, a condensate line configured to receive condensate from the condensed steam from the heat exchanger and to conduct the condensate away from the heat exchanger, a water supply line configured to supply water to the heat exchanger, a discharge line configured to receive heated water from the heat exchanger and to conduct the heated water away from the heat exchanger, a steam valve disposed on the steam supply line and configured to control the flow of steam through the steam supply line, a condensate valve disposed on the condensate line and configured to control the flow of condensate through the condensate line, a first sensor disposed downstream of the steam valve and upstream of the condensate valve and configured to output a pressure signal indicative of the pressure between the steam valve and the condensate valve in the steam system, and / or a second sensor located at the condensate outlet configured to output a condensate water temperature signal indicative of the temperature of the condensate water between the heat exchanger and the condensate valve in the condensate line, A third sensor is positioned on the water discharge line and configured to output a water temperature signal indicating the temperature of the heated water passing through the water discharge line, A steam system is disclosed, comprising a controller configured to control the opening and closing of a steam valve and a condensate valve based on a water temperature signal and at least one of a pressure signal and a condensate water temperature signal.

[0004] By controlling the flow in both the steam valve and the condensate valve based on the water temperature signal and at least one of the pressure signal and the condensate temperature signal, the system can simultaneously achieve (i) reliable supercooling of the condensate (meaning more heat is transferred from the steam to the water), resulting in a more efficient heating process, (ii) stable outlet water temperature even under rapid or dynamic demand load fluctuations, and (iii) a high turndown ratio for the system. When both the steam valve and the condensate valve are controlled based on the water temperature signal and the pressure signal, the system can further ensure that (iv) the system does not stall under any circumstances. In addition, dual control (i.e., control by both the steam valve and the condensate valve) allows the condensate to be supercooled more quickly when there are rapid demand load fluctuations from high to low demand loads, enabling faster and more efficient operation than otherwise.

[0005] The first sensor may be a pressure sensor. The first sensor may be positioned between the steam valve and the heat exchanger in the steam supply line so as to output a pressure signal indicating the pressure in the steam supply line downstream of the steam valve. The second sensor may be a temperature sensor. The third sensor may be a temperature sensor.

[0006] The controller may be configured to control the steam valve based on a water temperature signal and the condensate valve based on a pressure signal.

[0007] The controller may be configured to control the condensate valve based on a comparison of a pressure signal with a set pressure. The set pressure may be a setpoint pressure or a set pressure range, and the set pressure range is the range of acceptable pressures.

[0008] The controller may be configured to operate in a feedback loop to control the condensate valve to at least partially close when the pressure signal indicates that the pressure in the steam supply line is below a set pressure and not trending upward, and / or to control the condensate valve to at least partially open when the pressure signal indicates that the pressure in the steam supply line is above a set pressure and not trending downward.

[0009] If the set pressure is within the set pressure range, the pressure signal may indicate that the pressure is below the lower limit of the set pressure range. Similarly, the pressure signal may indicate that the pressure is above the upper limit of the set pressure range.

[0010] In other words, the controller may be a PID controller that can be configured to control the condensate valve based on a pressure signal compared to a setpoint pressure or a set pressure range.

[0011] The set pressure may be higher than the pressure obtained by adding the condensate pressure drop at the condensate valve to the pressure downstream of the condensate valve in the condensate line, in order to prevent stalling of the steam system.

[0012] If the set pressure is within the set pressure range, the lower limit of the set pressure range may be higher than the pressure obtained by adding the condensate pressure drop to the pressure downstream of the condensate valve in the condensate line.

[0013] The set pressure may be lower than the pressure obtained by subtracting the critical pressure drop of the steam valve from the steam supply pressure upstream of the steam valve.

[0014] If the set pressure is within the set pressure range, the upper limit of the set pressure range may be lower than the pressure obtained by adding the condensate pressure drop to the pressure downstream of the condensate valve in the condensate line.

[0015] The heat exchanger may be sized so that condensed water is reliably supercooled when the steam pressure between the steam valve and the heat exchanger is at the set pressure and the water flow rate is at maximum demand.

[0016] The maximum demand may be related to the mass flow rate of water passing through the heat exchanger and / or the water inlet temperature. In other words, the maximum demand may correspond to the maximum mass flow rate of water passing through the heat exchanger and / or the minimum inlet water temperature.

[0017] The controller may be configured to control the steam valve based on the water temperature signal and the condensate valve based on the condensate temperature signal.

[0018] The controller may be configured to control the condensate valve based on a comparison between the condensate temperature signal and the condensate set temperature.

[0019] The condensate set temperature may be a set point temperature or a set temperature range.

[0020] The controller may be configured to operate in a feedback loop to control the condensate valve to at least partially close when the condensate temperature signal is above the condensate set temperature and is not trending downwards, and / or to control the condensate valve to at least partially open when the condensate temperature signal is below the condensate set temperature and is not trending upwards.

[0021] If the set temperature is within the set temperature range, the condensate temperature signal may indicate that the temperature is below the lower limit of the set temperature range. Conversely, the condensate temperature signal may indicate that the temperature is above the set temperature range if it indicates that the temperature is above the upper limit of the set temperature range.

[0022] In other words, the controller may be a PID controller that can be configured to control the condensate valve based on a temperature signal compared to a setpoint temperature or a set temperature range.

[0023] The controller may control the condensate valve to an open degree that is not fully closed and is the minimum.

[0024] Since the measurement is performed downstream of the heat exchanger, if the condensate valve is fully closed, the true condensate water temperature cannot be measured.

[0025] The controller may be configured to control the steam valve based on a comparison between the water temperature signal and the set water temperature.

[0026] The set water temperature may be a set point water temperature or a set water temperature range.

[0027] The controller is controlled to at least partially open the steam valve when the water temperature signal is below the set point water temperature and has no upward trend, and / or is controlled to at least partially close the steam valve when the water temperature signal is above the set water temperature and has no downward trend, and may be configured to operate in a feedback loop.

[0028] When the set water temperature is a set water temperature range, when the water temperature signal indicates that the temperature is below the lower limit of the set water temperature range, the water temperature signal may indicate that the temperature is below the set water temperature range. When the water temperature signal indicates that the temperature is above the upper limit of the set water temperature range, the water temperature signal may indicate that the temperature is above the set water temperature range.

[0029] In other words, the controller may be a PID controller configured to control the steam valve based on the water temperature signal compared with the set point water temperature or the set water temperature range.

[0030] According to a second aspect, receiving a pressure signal or a condensate water temperature signal, receiving a water temperature signal, and controlling the opening and closing of the steam valve and the condensate valve based on at least one of the water temperature signal, the pressure signal, and the condensate water temperature signal, a method for controlling the steam system according to any one of the preceding claims is disclosed.

[0031] The method may include controlling a steam valve based on a water temperature signal and controlling a condensate valve based on a pressure signal.

[0032] The method may include controlling a condensate valve based on a comparison of a pressure signal with a set pressure.

[0033] The method may also include operating to control the steam valve and the condensate valve in a feedback loop by controlling the condensate valve to at least partially close when the pressure signal indicates that the pressure in the steam supply line is below a setpoint pressure and not trending upward, and / or to at least partially open when the pressure signal indicates that the pressure in the steam supply line is above a setpoint pressure and not trending downward.

[0034] The set pressure may be higher than the sum of the condensate pressure drop at the condensate valve and the pressure downstream of the condensate valve in the condensate line, in order to prevent stalling of the steam system. The set pressure may be lower than the pressure obtained by subtracting the critical pressure drop at the steam valve from the steam supply pressure upstream of the steam valve.

[0035] The method may include controlling a steam valve based on a water temperature signal and controlling a condensate valve based on a condensate temperature signal.

[0036] The method may include controlling a condensate valve based on a comparison between a condensate temperature signal and a set condensate temperature.

[0037] The method may also include operating in a feedback loop to control the condensate valve to at least partially close when the condensate temperature signal is above a set condensate temperature and is not trending downwards, and / or to control the condensate valve to at least partially open when the condensate temperature signal is below a set condensate temperature and is not trending upwards.

[0038] The method may include controlling the condensate valve to a minimum opening that does not completely close it.

[0039] The method may include controlling a steam valve based on a comparison between a water temperature signal and a set water temperature.

[0040] The method may include operating in a feedback loop to control the steam valve to at least partially open when the water temperature signal is below a setpoint water temperature and not trending upward, and / or to control the steam valve to at least partially close when the water temperature signal is above a setpoint water temperature and not trending downward.

[0041] According to the third aspect, The steam system is subject to the steam supply pressure of the environment in which it is installed, To determine the critical steam pressure drop before and after the steam valve, Determining the maximum demand load of the heat exchanger, A method for designing a steam system according to a first embodiment is disclosed, which includes selecting a heat exchanger size based on the steam supply pressure, the steam critical pressure, and the maximum demand load.

[0042] The method may further include receiving the condensate return pressure of the environment in which the steam system is installed, determining the condensate pressure drop before and after the condensate valve, and selecting the heat exchanger size based on the condensate return pressure and the condensate critical pressure.

[0043] The method may include selecting a set pressure for the heat exchanger inlet based on the steam supply pressure and the steam critical pressure, and selecting the heat exchanger size includes determining the heat exchanger size at which condensate is supercooled when the heat exchanger inlet pressure is the set pressure and when the maximum demand load occurs.

[0044] Those skilled in the art will understand that, except where mutually exclusive, any features or parameters described in relation to any one of the above embodiments may be applied to any other embodiment. Furthermore, except where mutually exclusive, any features or parameters described herein may be applied to any embodiment and / or combined with any other features or parameters described herein.

[0045] Here, an embodiment will be described as merely an example, with reference to the attached drawings. [Brief explanation of the drawing]

[0046] [Figure 1] This is a schematic diagram illustrating a first exemplary steam system for heating water. [Figure 2] This is a schematic diagram illustrating a second exemplary steam system for heating water. [Figure 3] This is a flowchart illustrating the steps of a basic method for heating water using an exemplary steam system. [Figure 4a] This flowchart shows a more detailed process for heating water using an exemplary steam system. [Figure 4b] This flowchart shows a more detailed process for heating water using an exemplary steam system. [Figure 5] This flowchart shows the steps of an exemplary method for designing exemplary steam systems such as those shown in Figures 1 and 2. [Modes for carrying out the invention]

[0047] Figure 1 shows a first exemplary steam system 100 configured to heat water, for example, in a household hot water system. The first exemplary steam system 100 includes a heat exchanger 12 configured to receive steam on the supply side 14 and water on the demand side 16, and to heat the water with steam. In this example, the steam and water remain separate.

[0048] In this example, the steam system 100 includes a steam supply line 18 configured to connect to a steam source 20. In this example, the steam supply line 18 is connected to the supply side inlet 22 (also called the steam inlet 22) of the heat exchanger 12 to supply steam to the supply side 14 of the heat exchanger 12. In this example, the steam source 20 may supply steam at a constant pressure, such as 400 kPa.

[0049] The steam supplied to the supply side 14 via the steam supply line 18 condenses as it passes through the supply side 14 and transfers heat to the demand side 16 of the heat exchanger 12.

[0050] In this example, the steam system 100 includes a condensate line 24 configured to connect to a condensate discharge section 26. The condensate line 24 is connected to a supply outlet 28 (also called a condensate outlet 28) and is configured to receive condensate (from condensed steam) from the supply side 14 of the heat exchanger 12, guide the condensate out of the heat exchanger 12, and send it to the condensate discharge section 26.

[0051] In some examples, the condensed water received at the condensed water discharge section 26 may be heated in another system, or it may be connected to a steam source 20 to form a closed-loop system that supplies steam to the steam source 20.

[0052] In this example, the steam system 100 includes a water supply line 30 configured to connect to the demand-side inlet 34 (also called the water inlet 34) of the demand-side 16 of the heat exchanger 12. The water supply line 30 is configured to supply water to the demand-side 16 of the heat exchanger 12. The water supplied to the water inlet 34 may be relatively cold water. In this example, the water supply line 30 is configured to connect to a water source 32, for example, a household water supply system.

[0053] In the heat exchanger 12, the water received on the demand side 16 is heated together with the steam received on the supply side 14. The steam condenses and exits the heat exchanger 12 as condensed water, and the water is heated and exits the heat exchanger 12 as heated water.

[0054] In this example, the steam system 100 includes a discharge line 36 connected to the demand-side outlet 38 (also called the water outlet 38) of the demand-side 16 of the heat exchanger 12, which receives heated water from the demand-side 16 of the heat exchanger 12 and directs the heated water from the heat exchanger 12 towards the drain 37. The water in the water inlet 34 is relatively cooler than the heated water at the water outlet 38 when the heat exchanger is operating to receive steam at the steam inlet 22.

[0055] In some cases, the drain 37 may be connected to the water source 32 in a closed loop by a household water supply system, for example. The heated water from the drain 37 can lose its heat by passing through the household water supply system and reach the water source 32 at a relatively low temperature.

[0056] In this example, the steam valve 40 is located on the steam supply line 18 and is configured to control the flow of steam through the steam supply line 18. The steam valve 40 may be, for example, a globe valve. In other examples, the steam valve may be any preferred valve such as a slide valve, piston valve, or ball valve. In this example, the steam valve 40 is connected to a controller 50 configured to control the opening and closing of the steam valve 40. In other words, the steam valve 40 may be actively controlled by the controller 50 to control the flow of steam through the steam supply line 18. In this example, the steam valve 40 is a variable control valve, which increases the mass flow rate of steam passing through the steam valve 40 by incrementally opening the steam valve 40, thereby supplying more steam to the supply side 14 of the heat exchanger 12, and decreases the mass flow rate of steam passing through the steam valve 40 by incrementally closing the steam valve 40, thereby supplying less steam to the supply side 14 of the heat exchanger 12. In this example, the steam valve 40 may be sized based on the pressure of the steam supplied by the steam source 20 so that at maximum opening, there is at least a critical pressure drop (i.e., a pressure drop at which the steam velocity does not increase even if the pressure drops further) before and after the steam valve 40. This ensures that the mass flow rate before and after the steam valve 40 is reduced by incrementally closing the steam valve 40 from its maximum opening, and as a result, the steam valve 40 can be used effectively across its entire opening range.

[0057] In this example, the condensate valve 42 is located on the condensate line 24 and is configured to control the flow of condensate through the condensate line 24. In this example, the condensate valve 42, like the steam valve 40, is connected to a controller 50 configured to control the opening and closing of the condensate valve 42. In other examples, the condensate valve 42 and the steam valve 40 may be different types of valves with different control methods.

[0058] In this example, the pressure sensor 44 is located in the steam supply line 18 between the steam valve 40 and the steam inlet 22 of the heat exchanger 12. The pressure sensor 44 is configured to output a pressure signal indicating the pressure in the steam supply line 18 downstream of the steam valve 40 (i.e., between the steam valve 40 and the heat exchanger 12). In some examples, the pressure sensor may be located anywhere downstream of the steam valve 40 and upstream of the condensate valve 42 to output a pressure signal indicating the pressure on the supply side 14 of the steam system between the steam valve 40 and the condensate valve 42. In other examples, the pressure sensor may be any type of sensor or set of sensors that can be used to indicate the pressure between the steam valve 40 and the condensate valve 42 in the steam system.

[0059] In this example, the water temperature sensor 46 is located on the water discharge line 36 and is configured to output a water temperature signal indicating the temperature of the heated water in the water discharge line 36. In other examples, the temperature sensor may be any type of sensor or set of sensors that can be used to indicate the temperature of the water in the water discharge line 36.

[0060] In this example, the controller 50 is configured to control the opening and closing of the steam valve 40 and the condensate valve 42 based on a water temperature signal and a pressure signal. By simultaneously controlling the steam valve 40 and the condensate valve 42, the liquid level (or height) of the condensate in the heat exchanger 12 can be controlled. For example, if the steam valve 40 is open and the condensate valve 42 is closed, or if the steam valve 40 is more open than the condensate valve 42, and the mass flow rate of steam before and after the steam valve 40 (and therefore entering the steam inlet 22) is greater than the mass flow rate of condensate before and after the condensate valve 42 (and therefore exiting the condensate outlet 28), the liquid level of the condensate in the heat exchanger will rise. Conversely, if the steam valve 40 is closed and the condensate valve 42 is open, or if the steam valve 40 is not more open than the condensate valve 42, and the mass flow rate of steam before and after the steam valve 40 (and therefore entering the steam inlet 22) is smaller than the mass flow rate of condensate before and after the condensate valve 42 (and therefore exiting the condensate outlet 28), the liquid level of condensate in the heat exchanger will decrease.

[0061] By controlling the liquid level of condensate in the heat exchanger 12, the area of ​​the heating surface receiving steam can be varied, thereby controlling the amount of heat conducted throughout the heat exchanger 12. By controlling the liquid level of condensate, the steam system 100 can ensure that the condensate is reliably supercooled in the heat exchanger 12 before it is discharged. This significantly reduces the amount of downstream flash steam, which can improve system performance and reduce heat loss. Furthermore, as the liquid level of condensate rises, heat transfer decreases, increasing the steam pressure in the heat exchanger 12. This provides sufficient pressure to discharge the condensate through the condensate valve 42, thus preventing the steam system 100 from stalling.

[0062] The heat exchanger may typically be sized to operate at a predetermined steam inlet pressure, at which pressure, the heat exchanger is configured to supercool condensate when there is a maximum demand for water. In some applications, the maximum demand corresponds to the maximum flow rate of water through the heat exchanger 12. In other applications, the maximum demand may correspond to the minimum inlet water temperature. In further applications, the maximum demand may relate to both the mass flow rate of water through the heat exchanger 12 and the minimum inlet water temperature. In this example, the heat exchanger 12 may be sized to operate at a predetermined steam inlet 22 pressure that is equal to or lower than the steam supply pressure upstream of the steam valve 40 minus the critical pressure drop of the steam valve 40, and is configured to supercool condensate when receiving steam below the predetermined steam inlet 22 pressure. This maximizes the efficiency of the steam system 100 by ensuring that condensate is always supercooled when the inlet pressure is maintained below the predetermined steam inlet pressure. Thus, this makes it possible for the steam system 100 to supercool condensate under all load conditions.

[0063] In this example, the steam between the steam valve 40 and the condensate valve 42 has a set pressure. In this example, the set pressure is a setpoint pressure, for example, X kPa. The setpoint pressure may be set to the same pressure as a predetermined steam inlet 22 pressure based on the size determination of the heat exchanger 12.

[0064] To ensure that the steam system 100 does not stall at any point (i.e., to ensure that the pressure upstream of the condensate valve 42 in the condensate line 24 is always high enough to allow a steam flow through the condensate valve 42 to the condensate discharge section 26), the set pressure is set to be higher than the sum of the condensate pressure drop at the condensate valve and the pressure downstream of the condensate valve 42 in the condensate line 24.

[0065] By setting the set pressure higher than the sum of the condensate pressure drop at the condensate valve and the pressure downstream of the condensate valve 42 in the condensate line 24, and lower than or equal to the steam supply pressure upstream of the steam valve 40 minus the critical pressure drop of the steam valve 40, it is ensured that the steam system 100 will not stall at any point and that the condensate will always be supercooled, thereby improving the reliability and efficiency of the system.

[0066] Therefore, as will be explained in more detail with reference to the flowcharts in Figures 3 and 4, the dual simultaneous control of the supply flow 14 into and out of the heat exchanger 12 at both the steam valve 40 and the condensate valve 42 based on the water temperature signal and pressure signal allows the system to simultaneously (i) ensure that the condensate is reliably supercooled (meaning that more heat from the steam is transferred to the water), resulting in a more efficient heating process; (ii) ensure that the outlet water temperature remains stable even under rapid or dynamic demand load fluctuations; (iii) achieve a high turndown ratio for the system; and (iv) ensure that the system does not stall under any conditions. Dual control (i.e., control by both the steam valve 40 and the condensate valve 42) also allows the condensate to be supercooled more quickly when there are rapid demand load fluctuations from high to low demand loads, thus enabling faster and more efficient operation than otherwise.

[0067] In this example, the controller 50 is configured to control the condensate valve 42 based on a comparison of a pressure signal with a setpoint pressure. The controller 50 in this example operates in a feedback loop to control the condensate valve 42 to control the pressure at the pressure sensor to the setpoint pressure. In other words, when the pressure signal indicates that the pressure needs to be increased, the controller 50 may control the condensate valve 42 to be at least partially closed, and when the pressure signal indicates that the pressure needs to be decreased, the controller 50 may control the condensate valve 42 to be at least partially open.

[0068] In some examples, the controller 50 may be a proportional integral derivative (PID) controller and is configured to operate in a feedback loop to control the condensate valve at least partially when the pressure signal indicates that the pressure in the steam supply line 18 is below a set pressure and not trending upward, and to control the condensate valve at least partially when the pressure signal indicates that the pressure in the steam supply line is above a set pressure and not trending downward. This takes into account the delay time between making a change to the condensate valve 42 and observing that change. The PID controller may also control the amount of partial opening and closing of the condensate valve 42 based on the difference between the steam pressure and the set pressure and the rate of change of the steam pressure.

[0069] In other examples, the set pressure may be a set pressure range that encompasses an acceptable range of pressures, such as Y~Z kPa, and the condensate valve 42 may be controlled so that the pressure between the steam valve 40 and the condensate valve 42 is reliably within the set pressure range. When the set pressure is a set pressure range, the pressure signal may indicate that the pressure is below the set pressure range when the pressure signal indicates that the pressure is below the lower limit of the set pressure range. The pressure signal may indicate that the pressure is above the set pressure range when the pressure signal indicates that the pressure is above the upper limit of the set pressure range.

[0070] If the set pressure is within the set pressure range, the lower limit of the set pressure range may be set higher than the pressure obtained by adding the condensate pressure drop to the pressure downstream of the condensate valve 42 in the condensate line 24. In such an example, the upper limit of the set pressure range may be less than or equal to the pressure obtained by subtracting the critical pressure drop of the steam valve 40 from the steam supply pressure upstream of the steam valve 40.

[0071] In this example, the controller 50 is further configured to control the steam valve 40 based on a comparison between the water temperature signal and the set water temperature. In this example, the set water temperature is the setpoint water temperature, for example, 60 degrees Celsius.

[0072] In this example, the controller 50 operates in a feedback loop to control the steam valve 40 to control the temperature at the water temperature sensor 46 (in the discharge line 36) to a setpoint water temperature. In other words, when the water temperature signal indicates that the water temperature needs to be raised (i.e., the water temperature is below the setpoint water temperature), the controller 50 may control the steam valve 40 to open at least partially, and when the water temperature signal indicates that the water temperature needs to be lowered (i.e., the water temperature is above the setpoint water temperature), the controller 50 may control the steam valve 40 to close at least partially.

[0073] In this example, the controller 50 is a PID (proportional-integral-derivative) controller and is configured to operate in a feedback loop to control the steam valve 40 at least partially when the water temperature signal indicates that the water temperature in the discharge line 36 is above the setpoint water temperature and is not trending downwards, and to control the steam valve 40 at least partially when the water temperature signal indicates that the pressure water temperature in the discharge line 36 is below the setpoint water temperature and is not trending upwards. This takes into account the delay time between making a change to the steam valve 40 and observing that change. The PID controller may also control the amount of partial opening and closing of the steam valve 40 based on the deviation of the water temperature from the setpoint water temperature and the rate of change of the water temperature.

[0074] In some cases, the set water temperature may be a set water temperature range that encompasses an acceptable temperature range, such as 55 to 65 degrees Celsius. In such cases, the water temperature signal may indicate that the temperature is below the set water temperature range when the water temperature signal indicates that the temperature is below the lower limit of the set water temperature range. The water temperature signal may indicate that the temperature is above the set water temperature range when the water temperature signal indicates that the temperature is above the upper limit of the set water temperature range.

[0075] Figure 2 shows a second exemplary steam system 200. The second exemplary steam system 200 is similar to the first exemplary steam system 100, and the same reference numerals indicate similar features. The second exemplary steam system 200 differs from the first exemplary steam system 100 in that it does not have a pressure sensor and has a condensate temperature sensor 48 located at the condensate outlet 28 on the condensate line 24 (i.e., between the condensate outlet 28 and the condensate valve 42) and configured to output a condensate temperature signal indicating the temperature of the condensate in the condensate line 24 between the heat exchanger 12 and the condensate valve 42. In other examples, the condensate temperature sensor may be any type of sensor or set of sensors that can be used to indicate the temperature in the condensate line 24.

[0076] In yet another example, the steam system may include both a pressure sensor 44, as in the first exemplary steam system 100, and a condensate temperature sensor 48, as in the second exemplary steam system 200.

[0077] In this example, the controller 50 is configured to control the opening and closing of the steam valve 40 and the condensate valve 42 based on the water temperature signal and the condensate water temperature signal. By controlling the steam valve 40 and the condensate valve 42 based on the condensate water temperature signal, the temperature of the condensate is directly controlled, enabling reliable supercooling of the condensate in the steam system 200. Furthermore, by controlling the steam valve 40 and the condensate valve 42 based on the water temperature signal, the outlet water temperature remains stable even under rapid or dynamic demand load fluctuations, resulting in a high turndown ratio for the system 200, similar to the first exemplary steam system 100. In the second exemplary steam system 200, the pressure on the supply side 14 is not directly controlled, making it more prone to stalling than the first exemplary steam system 100.

[0078] The controller 50 in this example may be configured to operate in a feedback loop to control the steam valve 40 to control the temperature at the temperature sensor (in the discharge line 36) to a setpoint water temperature, similar to the first exemplary steam system 100.

[0079] The controller 50 of the second exemplary steam system 200 differs from the controller of the first exemplary steam system 100 in that it is configured to control the condensate valve 42 based on a comparison of the condensate temperature signal with the condensate set temperature.

[0080] In this example, the condensate set temperature is a setpoint condensate temperature, such as 90 degrees Celsius. Ideally, for reliable supercooling of the condensate, the setpoint condensate temperature is below 100 degrees Celsius. In this example, the controller 50 operates in a feedback loop to control the condensate valve 42 to control the condensate temperature at the condensate temperature sensor 48 to the setpoint condensate temperature. In other words, when the condensate temperature signal indicates that the condensate temperature needs to be lowered (i.e., the condensate temperature is determined to be above the setpoint condensate temperature based on the condensate temperature signal), the controller 50 may be controlled to at least partially close the condensate valve 42, and when the condensate temperature signal indicates that the condensate temperature needs to be raised (i.e., the condensate temperature is determined to be below the setpoint condensate temperature based on the condensate temperature signal), the controller 50 may be controlled to at least partially open the condensate valve 42.

[0081] In some examples, the controller 50 may be a PID controller and is configured to operate in a feedback loop to control the condensate valve 42 to at least partially open when the condensate temperature signal indicates that the condensate temperature is below the set condensate temperature and is not trending upward, and to at least partially close when the condensate temperature signal indicates that the condensate temperature is above the setpoint condensate temperature and is not trending downward. This takes into account the delay time between making a change to the condensate valve 42 and observing that change. The PID controller may control the amount of partial opening and closing of the condensate valve 42 based on the difference between the condensate temperature and the set condensate temperature and the rate of change of the condensate temperature.

[0082] In other examples, the set condensate temperature may be a set condensate temperature range that can encompass an acceptable temperature range, such as 85 to 90 degrees Celsius, and the condensate valve 42 may be controlled so that the condensate temperature between the heat exchanger 12 and the condensate valve 42 is reliably within the set condensate temperature range. When the set condensate temperature is within the set condensate temperature range, the condensate temperature signal may indicate that the condensate temperature is below the lower limit of the set condensate temperature range. The condensate temperature signal may indicate that the condensate temperature is above the set condensate temperature range when the condensate temperature signal indicates that the condensate temperature is above the upper limit of the set condensate temperature range.

[0083] In this example, if the condensate temperature is monitored by the condensate temperature sensor 48, the controller 50 may be configured to control the condensate valve 42 to a minimum opening that does not completely close it. Since the measurement is taken downstream of the heat exchanger 12, closing the condensate valve 42 would prevent the condensate from flowing out of the heat exchanger 12, so if the condensate valve 42 is completely closed, the true condensate temperature cannot be measured.

[0084] Figure 3 is a flowchart showing the basic steps of a method 300 for controlling a steam system, such as the first exemplary steam system 100 or the second exemplary steam system 200.

[0085] In block 302, method 300 includes the controller 50 receiving a pressure signal in a first exemplary steam system 100 or a condensate temperature signal in a second exemplary steam system 200. In some examples combining the first and second exemplary steam systems 100, 200, the controller 50 may receive both a pressure signal and a condensate temperature signal.

[0086] In block 304, method 300 includes the controller 50 receiving a water temperature signal. Blocks 302 and 304 may be performed simultaneously or sequentially in any order.

[0087] In block 306, method 300 includes controlling the opening and closing of the steam valve 40 and the condensate valve 42 based on a water temperature signal received by the controller 50 and at least one of the received pressure signal and condensate water temperature signal.

[0088] Figures 4a and 4b are flowcharts illustrating a more detailed and exemplary method 400 for controlling steam systems 100 and 200. Figures 4a and 4b are configured to run concurrently, but may run sequentially. Figure 4a begins at block 302 of Figure 3, and Figure 4b begins at block 304 of Figure 3.

[0089] From block 302, the method 400 in this example is configured to control the condensate valve 42 based on a pressure signal and / or a condensate temperature signal. From block 304, the method 400 in this example is configured to control the steam valve 40 based on a water temperature signal.

[0090] From block 302, method 400 proceeds to control the condensate valve 42 based on a comparison between a pressure signal and a set pressure, or a comparison between a condensate temperature signal and a set condensate temperature. In this example, from block 302, method 400 proceeds to block 402, where it is determined whether the pressure needs to be increased or the condensate temperature needs to be decreased. In other words, if there is a set pressure, block 402 determines whether the pressure signal indicates that the pressure is below the set pressure, and if there is a set condensate temperature, block 402 determines whether the condensate temperature signal indicates that the condensate temperature is above the set condensate temperature.

[0091] If it is determined that the pressure is below the set pressure or the condensate temperature is above the set condensate temperature, the method proceeds to block 404, controls the condensate valve 42 to close (e.g., incrementally), and returns to block 302 as a feedback loop. If the controller 50 is a PID controller, determining whether the pressure needs to be increased may include determining whether the pressure signal indicates that the pressure in the steam supply line is below the setpoint pressure and is not trending upward (i.e., the derivative of the pressure signal over time shows a negative trend), and determining whether the condensate temperature needs to be decreased may include determining whether the condensate temperature signal indicates that the condensate temperature is above the set condensate temperature and is not trending downward (i.e., the derivative of the pressure signal over time shows a positive trend).

[0092] If it is determined that there is no need to increase the pressure or decrease the condensate temperature, method 400 proceeds to block 406. In block 406, method includes determining whether there is a need to decrease the pressure or increase the condensate temperature. If it is determined that there is a need to decrease the pressure or increase the condensate temperature, method proceeds to block 408, controls the condensate valve 42 to open (e.g., incrementally), and returns to block 302 as a feedback loop. If controller 50 is a PID controller, determining whether there is a need to decrease the pressure may include determining whether the pressure signal indicates that the pressure in the steam supply line is above the setpoint pressure and is not decreasing (i.e., the derivative of the pressure signal over time shows a positive trend), and determining whether there is a need to increase the condensate temperature may include determining whether the condensate temperature signal indicates that the condensate temperature is below the setpoint condensate temperature and is not increasing (i.e., the derivative of the pressure signal over time shows a negative trend).

[0093] If, in block 406, it is determined that there is no need to lower the pressure or raise the condensate temperature, method 400 proceeds to block 410, where the condensate valve 42 is not controlled to change its opening, and returns to block 302 as a feedback loop. If the controller is a PID controller, the pressure or condensate temperature may have already increased or decreased due to the previous control, so the condensate valve 42 may not be controlled to open or close even if the pressure is below or above the set pressure, or the condensate temperature is below or above the set condensate temperature. Therefore, a PID controller capable of monitoring the derivatives of the pressure signal and / or condensate signal can be used to account for the delay time between controlling the condensate valve 42 and observing the change in the state of the steam system. The PID controller may also control the amount of opening and closing of the condensate valve 42 based on the difference between the condensate temperature and the set condensate temperature and the rate of change in the condensate temperature.

[0094] When the controller 50 receives a condensate temperature signal (for example, in the second exemplary steam system 200), an additional block may be present between block 402 and block 404 to determine whether further incremental closing of the condensate valve 42 would completely close it, or whether the condensate valve is at its minimum opening. If it is determined that the condensate valve 42 would be completely closed, or that it is already at its minimum opening, the method may proceed directly to block 410 to avoid controlling the condensate valve to close completely or beyond its minimum opening. This ensures that the outflow from the heat exchanger 12 is not obstructed, allowing for continued and accurate measurement of the condensate temperature.

[0095] From block 304, method 400 proceeds to control the steam valve 40 based on a comparison of the water temperature signal with the set water temperature. In this example, from block 304, method 400 proceeds to block 412, where it is determined whether or not the water temperature needs to be increased. In other words, block 412 determines whether or not the water temperature signal indicates that the water temperature is below the set water temperature.

[0096] If it is determined that the water temperature is below the set water temperature, the method proceeds to block 414, which controls the steam valve 40 to open (for example, incrementally), and returns to block 304 as a feedback loop. If the controller 50 is a PID controller, determining whether or not the water temperature needs to be raised may also include determining whether the water temperature signal indicates that the water temperature is below the set point water temperature and is not trending upward (i.e., the derivative of the water temperature signal over time shows a negative trend).

[0097] If it is determined that there is no need to raise the water temperature, method 400 proceeds to block 416. In block 416, method includes determining whether or not there is a need to lower the water temperature. If it is determined that there is a need to lower the water temperature, method proceeds to block 418, controls the steam valve 40 to close (for example, incrementally), and returns to block 304 as a feedback loop. If controller 50 is a PID controller, determining whether or not there is a need to lower the water temperature may also include determining whether the water temperature signal indicates that the water temperature in the discharge line 36 is above the setpoint water temperature and is not trending downward (i.e., the derivative of the water temperature signal over time shows a positive trend).

[0098] If it is determined in block 416 that there is no need to lower the water temperature, method 400 proceeds to block 420, where the steam valve 40 is not controlled to change its opening, and the process returns to block 304 as a feedback loop. If the controller is a PID controller, the water temperature may have already risen or fallen due to the previous control, so it is not necessary to control the steam valve 40 to open or close even if the water temperature is below or above the set water temperature. Therefore, a PID controller capable of monitoring the derivative of the water temperature signal can be used to account for the delay time between controlling the steam valve 40 and observing the change in the state of the steam system. The PID controller may also control the amount of opening and closing of the steam valve 40 based on the difference between the water temperature and the setpoint water temperature and the rate of change in water temperature.

[0099] Figure 5 is a flowchart showing the steps of Method 500 for designing a steam system, such as a first exemplary steam system 100 or a second exemplary steam system 200.

[0100] In block 502, the method includes receiving the steam supply pressure of the environment in which the steam system is installed. In block 504, the method includes determining the critical pressure drop before and after the steam valve 40.

[0101] In block 506, the method may include receiving the condensate return pressure of the environment in which the steam system is installed. In block 508, the method may include determining the condensate pressure drop before and after the condensate valve 42. In some examples, blocks 506-508 may be omitted.

[0102] In block 510, the method includes determining the maximum demand load of the heat exchanger. This may be based on the maximum mass flow rate of water passing through the system and / or the maximum temperature difference between the water inlet 34 of the heat exchanger 12 and the set water temperature.

[0103] In block 512, the method includes selecting a heat exchanger size based at least on the steam supply pressure, the steam critical pressure drop, and the maximum demand load, and optionally further on the condensate return pressure and condensate pressure drop. For example, the heat exchanger may be sized to ensure that the condensate is subcooled at the maximum demand load, and the inlet steam pressure is at a set pressure less than or equal to the steam supply pressure minus the critical pressure drop. The set pressure may also be based on the condensate return pressure and condensate pressure drop. For example, the set pressure may exceed the pressure obtained by adding the condensate return pressure to the condensate pressure drop.

[0104] The present invention is not limited to the embodiments described above, and it will be understood that various modifications and improvements can be made without departing from the concepts described herein. Any feature may be used alone or in combination with any other feature, except where mutually exclusive, and this disclosure extends to and includes all combinations and partial combinations of one or more features described herein.

Claims

1. A steam system configured to heat water, A heat exchanger configured to receive steam and water, wherein the steam is configured to heat the water, A steam supply line configured to be connected to a steam source in order to supply steam to the heat exchanger, A condensate line configured to receive condensate from condensed steam from the heat exchanger and to guide the condensate from the heat exchanger, A water supply line configured to supply water to the heat exchanger, A water discharge line configured to receive heated water from the heat exchanger and guide the heated water from the heat exchanger, A steam valve is positioned on the steam supply line and configured to control the flow of steam passing through the steam supply line, A condensate valve is positioned on the condensate line and configured to control the flow of condensate through the condensate line, A first sensor located downstream of the steam valve and upstream of the condensate valve, configured to output a pressure signal indicating the pressure between the steam valve and the condensate valve in the steam system, and / or a second sensor located at the condensate outlet, configured to output a condensate temperature signal indicating the temperature of the condensate between the heat exchanger and the condensate valve in the condensate line, A third sensor is positioned on the water discharge line and configured to output a water temperature signal indicating the temperature of the heated water passing through the water discharge line, A steam system comprising: a controller configured to control the opening and closing of the steam valve and the condensate water valve based on the water temperature signal and at least one of the pressure signal and the condensate water temperature signal.

2. The steam system according to claim 1, wherein the controller is configured to control the steam valve based on the water temperature signal and the condensate valve based on the pressure signal.

3. The steam system according to claim 2, wherein the controller is configured to control the condensate valve based on a comparison of the pressure signal with a set pressure.

4. The steam system according to claim 3, wherein the controller is configured to operate in a feedback loop to control the condensate valve at least partially when the pressure signal indicates that the pressure in the steam supply line is below the set pressure and not increasing, and / or to control the condensate valve at least partially when the pressure signal indicates that the pressure in the steam supply line is above the set pressure and not decreasing.

5. The steam system according to claim 3 or 4, wherein the set pressure is higher than the pressure obtained by adding the condensate pressure drop of the condensate valve to the pressure downstream of the condensate valve in the condensate line in order to prevent the steam system from stalling.

6. The steam system according to any one of claims 3 to 5, wherein the set pressure is lower than the pressure obtained by subtracting the critical pressure drop of the steam valve from the steam supply pressure upstream of the steam valve.

7. The steam system according to any one of claims 3 to 6, wherein the heat exchanger is sized such that the condensed water is reliably supercooled when the steam pressure between the steam valve and the heat exchanger is at the set pressure and the water flow rate is at maximum demand.

8. The steam system according to claim 1, wherein the controller is configured to control the steam valve based on the water temperature signal and the condensate valve based on the condensate water temperature signal.

9. The steam system according to claim 8, wherein the controller is configured to control the condensate valve based on a comparison between the condensate temperature signal and the condensate set temperature.

10. The steam system according to claim 9, wherein the controller is configured to operate in a feedback loop to control the condensate valve to at least partially close when the condensate temperature signal is above the condensate set temperature and is not decreasing, and / or to control the condensate valve to at least partially open when the condensate temperature signal is below the condensate set temperature and is not increasing.

11. The steam system according to claim 10, wherein the controller controls the condensate valve to the minimum opening that does not completely close it.

12. The steam system according to any one of claims 2 to 11, wherein the controller is configured to control the steam valve based on a comparison between the water temperature signal and a set water temperature.

13. The steam system according to claim 12, wherein the controller is configured to operate in a feedback loop to control the steam valve to at least partially open when the water temperature signal is below the setpoint water temperature and not trending upward, and / or to control the steam valve to at least partially close when the water temperature signal is above the setpoint water temperature and not trending downward.

14. Receiving the aforementioned pressure signal or the aforementioned condensed water temperature signal, Receiving the aforementioned water temperature signal, The opening and closing of the steam valve and the condensate valve are controlled based on the water temperature signal and at least one of the pressure signal and the condensate water temperature signal. A method for controlling a steam system according to any one of claims 1 to 13, including the method described above.

15. The method according to claim 14, comprising controlling the steam valve based on the water temperature signal and controlling the condensate valve based on the pressure signal.

16. The method according to claim 15, comprising controlling the condensate valve based on a comparison of the pressure signal with a set pressure.

17. The method according to claim 16, comprising controlling the steam valve and the condensate valve in a feedback loop by controlling the condensate valve to at least partially close when the pressure signal indicates that the pressure in the steam supply line is below the setpoint pressure and not trending upward, and / or to at least partially open when the pressure signal indicates that the pressure in the steam supply line is above the setpoint pressure and not trending downward.

18. The method according to claim 16 or 17, wherein the set pressure is higher than the pressure obtained by adding the condensate pressure drop of the condensate valve to the pressure downstream of the condensate valve in the condensate line in order to prevent stalling of the steam system.

19. The method according to any one of claims 16 to 18, wherein the set pressure is lower than the pressure obtained by subtracting the critical pressure drop of the steam valve from the steam supply pressure upstream of the steam valve.

20. The method according to claim 14, comprising controlling the steam valve based on the water temperature signal and controlling the condensate valve based on the condensate water temperature signal.

21. The method according to claim 20, comprising controlling the condensate valve based on a comparison between the condensate temperature signal and a set condensate temperature.

22. The method according to claim 21, comprising operating in a feedback loop to control the condensate valve to at least partially close when the condensate temperature signal is above the set condensate temperature and is not decreasing, and / or to control the condensate valve to at least partially open when the condensate temperature signal is below the set condensate temperature and is not increasing.

23. The method according to claim 22, comprising controlling the condensate valve to a minimum opening that does not completely close it.

24. The method according to any one of claims 15 to 23, comprising controlling the steam valve based on a comparison between the water temperature signal and a set water temperature.

25. The method according to claim 24, comprising operating in a feedback loop to control the steam valve to at least partially open when the water temperature signal is below the setpoint water temperature and not trending upward, and / or to control the steam valve to at least partially close when the water temperature signal is above the setpoint water temperature and not trending downward.

26. The steam system is subjected to the steam supply pressure of the environment in which it is installed, To determine the critical steam pressure drop before and after the steam valve, Determining the maximum demand load of the heat exchanger, The heat exchanger size is selected based on the steam supply pressure, the steam critical pressure, and the maximum demand load. A method for designing the steam system according to claim 1, including the following:

27. The steam system is subjected to condensate return pressure in the environment in which it is installed, To determine the condensate pressure drop before and after the condensate valve, The heat exchanger size is selected based on the aforementioned condensate return pressure and the aforementioned condensate critical pressure. The method according to claim 26, further comprising:

28. This includes selecting a set pressure at the inlet of the heat exchanger based on the steam supply pressure and the steam critical pressure, The method according to claim 26 or 27, wherein selecting the heat exchanger size includes determining the heat exchanger size at which condensate is supercooled when the inlet pressure of the heat exchanger is the set pressure and when the maximum demand load is present.

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