Temperature control system

Abstract

A temperature control system for controlling the temperature of a load and a method for controlling such a system. The temperature control system for controlling the temperature of a load comprises a refrigeration system configured to pump a refrigerant around a refrigerant circuit. The refrigerant circuit includes an evaporator couplable to the load, a compressor, a condenser, and an expansion zone downstream of an expansion device. The refrigerant circuit further comprises a by-pass channel allowing refrigerant to by-pass the condenser. A cooling capacity of the refrigeration system is controllable with continuous variability by varying the proportion of refrigerant circulating via the by-pass channel.

Description

[0001] Temperature control system

[0002] Technical Field

[0003] This invention relates to a temperature control system for controlling the temperature of a load and a method for controlling such a system.

[0004] Background

[0005] Temperature control systems that are capable of cooling a load are commonly used in laboratory and industrial equipment. Preferably, such systems are capable of accurately controlling the operating temperatures of equipment and storage temperatures of products. For example, a temperature control system may be employed to control the temperature of a water bath in a laboratory chiller. Users of temperature control systems are becoming increasingly aware of the environmental impact of temperature control systems, resulting from the energy that is required to accurately control the temperature of a load.

[0006] Existing temperature control systems based on a standard vapour-compression refrigeration system comprising an evaporator, compressor, condenser and expansion device may operate the compressor intermittently to control the amount of cooling provided by the system. However, intermittent compressor usage may result in more rapid degradation of the compressor compared to a system in which the compressor operates continuously. In some systems the compressor speed may be altered during use, but again there is increased wear on the compressor compared to a continuously operating state.

[0007] Some existing temperature control systems operate at a constant compressor speed. Such systems typically include a heater to balance the amount of cooling provided by the refrigeration portion of the system, and thereby control the amount of cooling provided by the temperature control system. Such a temperature control system may provide its maximum cooling effect when the system’s heater is switched off. The amount of cooling effect on the load may be reduced from the maximum cooling effect by intermittently adding heat from the heater to a load to control the temperature of the load. When the maximum cooling effect provided by the refrigeration system is much higher than the cooling requirements for the load, the temperature control system becomes inefficient. This is because significant additional heat needs to be added to the load by the heater to counteract the excess amount of cooling provided by the refrigeration system.

[0008] In some existing refrigeration systems, it is known to provide a by-pass that allows refrigerant to avoid flowing through the condenser. Such by-passes are used to rapidly increase temperature, for example during a defrost process, and are controlled by an on-off valve, for example a solenoid valve. In such existing systems, the on-off valve has a binary mode of operation such that either a maximum proportion of refrigerant may flow through the valve when the valve is on and open, or no refrigerant may flow through the valve when the valve is off and closed.

[0009] It is desirable to develop a temperature control system capable of accurately controlling the temperature of a load but with lower energy consumption.

[0010] Summary of the Invention

[0011] The invention may provide a temperature control system, and a method of controlling a temperature control system as defined in the appended independent claims. Optional features of the invention are set out in dependent sub-claims.

[0012] Thus, a temperature control system for controlling the temperature of a load comprises a refrigeration system configured to pump a refrigerant around a refrigerant circuit. The refrigerant circuit includes an evaporator couplable to the load, a compressor, a condenser, and an expansion zone downstream of an expansion device. The refrigerant circuit further comprises a by-pass channel allowing refrigerant to by-pass the condenser. A cooling capacity of the refrigeration system is controllable with continuous variability by varying the proportion of refrigerant circulating via the by-pass channel.

[0013] Other than the by-pass channel, the refrigeration system preferably operates in substantially the same way as a conventional vapour-compression refrigeration system. Thus, the evaporator preferably receives and evaporates a low pressure, low temperature liquid / vapour mixture from the expansion device. The compressor preferably receives and compresses low pressure, low temperature gas from the evaporator. The condenser preferably receives and condenses high pressure, high temperature gas from the compressor. The expansion device preferably receives and expands high pressure, low temperature liquid from the condenser. Thus, the basis of the cooling effect provided by the refrigeration system is well-understood by the person skilled in the art.

[0014] The compressor preferably acts as a pump to pump the refrigerant around the refrigeration circuit. The compressor may be configured to operate continuously. Advantageously, continuous operation reduces damage to the compressor resulting from intermittent usage. The compressor may be configured to operate at an unvarying speed. This may simplify control of the system and further reduce wear damage to the compressor.

[0015] The expansion device may be any means suitable to cause expansion of the hot liquid refrigerant formed in the condenser. For example, the expansion device may comprise a capillary tube, an orifice plate or an expansion valve. For example, the expansion device may be a thermostatic expansion valve or an electronic expansion valve.

[0016] The by-pass channel is configured to allow high temperature gaseous refrigerant that has passed through the compressor to by-pass the condenser and mix with the low temperature liquid refrigerant exiting the expansion device. Because any portion of refrigerant passing through the by-pass channel does not pass through the condenser, this portion of refrigerant is not cooled to the same degree, and a greater proportion of heat is retained within the refrigerant circuit.

[0017] The refrigerant circuit may further comprise a drier for receiving high pressure liquid from the condenser and removing moisture from the high pressure liquid.

[0018] The temperature control system removes heat from a load. Thus, the temperature control system may be described as a refrigerated temperature control system. The amount of heat that the temperature control system removes from the load may be described as a cooling capacity. The temperature control system may have a cooling capacity that is equivalent to the amount of heat that the evaporator is able to remove from a load while the system is operating. An absolute numerical value for cooling capacity of the system may depend on many factors, for example compressor speed, temperature of the load, and ambient temperature. It may be more useful to consider a relative cooling capacity. For example, a maximum cooling capacity for the temperature control system may be defined as the cooling capacity of the system when 0% of the refrigerant in the system flows through the by-pass channel. Conversely, a minimum cooling capacity for the temperature control system may be defined as the cooling capacity of the system when 100% of the refrigerant in the system flows through the by-pass channel.

[0019] The cooling capacity may be controllable between a first cooling capacity and a second cooling capacity. The first cooling capacity may be the maximum cooling capacity available when 0% of the refrigerant circulates via the by-pass channel (i.e. 100% of the refrigerant circulates via the condenser).

[0020] The second cooling capacity may be less than 20% of the first cooling capacity, for example less than 10%, or 5%, or 2%, or 1% of the first cooling capacity. The second cooling capacity may be the minimum cooling capacity of the temperature control system when 100% of refrigerant is circulated via the by-pass channel (i.e. 0% of the refrigerant circulates via the condenser). Advantageously, the cooling capacity may be adjusted between the first cooling capacity and second cooling capacity to match the cooling requirements of the load. For example, if the maximum cooling capacity of the system under specific conditions is 300 W and the cooling capacity required to maintain a load at a temperature of 20.6 °C is 177.3 W, then the proportion of refrigerant circulating via the by-pass may be varied to reduce the cooling capacity of the temperature control system from 300 W to 177.3 W. Then, if heat entering the load increases, the cooling capacity required to maintain the desired temperature may increase to 277.7 W. In this circumstance, the proportion of refrigerant circulating via the by-pass would be varied to increase the cooling capacity of the system to 277.7 W.

[0021] The cooling capacity may be continuously variable by continuously varying the proportion of refrigerant that circulates via the by-pass channel. Depending on the intended use of the temperature control system, the cooling capacity may be into the thousands of Watts. For example, the cooling capacity of a temperature control system may be continuously variable between 0W and 3000W, for example between 0W and 2000W or between 0W and 100W, or between 50W and 400W.

[0022] The proportion of refrigerant circulating via the by-pass channel may be controlled by at least one continuously variable metering device. The at least one continuously variable metering device may be located in the by-pass channel. A second valve may further be located in the by-pass channel. The second valve in the by-pass channel may advantageously prevent leakage through the continuously variable metering device in the by-pass channel.

[0023] The proportion of refrigerant circulating via the by-pass channel may variable between 0% and 100%, for example between 0% and 90%, for example between 1% and 90%, for example between 0% and 80%, for example between 1% and 80%, for example between 0% and 75%.

[0024] Advantageously, a continuously variable metering device may instead allow for continuous control between no refrigerant flowing through the device and a maximum proportion of refrigerant flowing through the device.

[0025] The refrigerant circuit may comprise a further valve outside of the by-pass channel. For example, a further valve may be located between a by-pass channel inlet and the condenser. The further valve may advantageously allow all of the refrigerant to circulate via the by-pass channel.

[0026] The at least one continuously variable metering device may have a continuously variable orifice size. The at least one continuously variable metering device may be an electronic expansion valve. A first return path may be defined from a compressor output to an evaporator inlet through the condenser and the expansion device. The first return path may form a portion of a standard vapour compression system. A second return path may be defined from a compressor output to an evaporator inlet via the by-pass channel. The amount of heat that can be extracted from a load, i.e. the cooling capacity of the system, may be controlled by continually controlling the proportion of refrigerant flowing via the first return path relative to the proportion of refrigerant flowing via the second return path.

[0027] Temperature control systems may be configured to control temperatures of a load within a wide range of target load temperatures. For example, embodiments of the temperature control system may be configured to control the temperature of the load to a target load temperature within the range of -50 °C and 150 °C, for example between -20 °C and 110 °C, for example between 0 °C and 100 °C .

[0028] Advantageously, the temperature control system may control the temperature of the load with precision. For example, the temperature control system may be configured to control the temperature of the load to within ± 1 °C of the target load temperature, preferably to within ± 0.5 °C of the target load temperature, preferably to within ± 0.2 °C of the target load temperature, preferably to within ± 0.1 °C of the target load temperature, preferably to within ± 0.05 °C of the target load temperature. Preferably, such precise control of the temperature is achieved without the use of a heater acting the load in order to balance the cooling effect of the refrigeration system.

[0029] The cooling capacity of the temperature control system may be variably controllable between 150W and 400W when the target load temperature is between 10 °C and 30 °C. The cooling capacity may variably controllable between 50W and 200W when the target load temperature is between -20 °C and 0 °C.

[0030] A coefficient of performance (COP) of the temperature control system may variable between 0.5 and 4, for example between 1 and 3.5. The coefficient of performance may be defined as the ratio of the cooling capacity to the power input to the refrigeration system. Power input to the refrigeration system is the power input required to power the evaporator, compressor, condenser and expansion device. For example, the temperature control system may have a cooling capacity of 400W and the power input required to provide this cooling capacity may be 100W. The coefficient of performance in this example is 400W (cooling capacity) 100W (power input) = 4.

[0031] In existing systems that lack a by-pass channel and control temperature of a load solely by a balancing addition of heat from a heater, a temperature control system may have a maximum cooling capacity of 400W. However, the load to be cooled may only require 25W of cooling. The power input to power the evaporator, compressor, condenser and expansion device may be 100W. Thus, to achieve the required cooling capacity of 25W, the heater must add a further 375W of heat to balance the maximum cooling capacity of 400W. In this system, the COP of system is 25W (required cooling capacity) -? [100W + 375W] (power input and heater input) = 0.05.

[0032] In contrast, the temperature control system according to the present disclosure may be able to reduce its cooling capacity from the maximum cooling capacity to match, or substantially match, the cooling requirements of the load. Even if the system comprises an additional heater to balance the cooling capacity, the amount of balancing heat needed is minimal and the coefficient of performance is high. Preferably, the temperature control system is able to control temperature precisely without use of an additional heater to balance the cooling capacity.

[0033] The temperature control system preferably comprises a temperature sensor for measuring a temperature of the load. The temperature control system may comprise more than one temperature sensor for measuring a temperature of the load. The, or each, temperature sensor may be a PT-1000 temperature sensor.

[0034] The temperature control system preferably comprises a controller. The controller may be configured to control the proportion of refrigerant flowing via the by-pass channel, for example in response to one or more feedback. In preferred embodiments, the controller may be electrically coupled to at least one temperature sensor for measuring temperature of the load and at least one continuously variable metering device arranged to control the proportion of refrigerant flowing via the by-pass channel. Thus, the temperature control system may use the temperature sensor to continuously measure the temperature of the load and feedback the temperature measurements to the controller. The controller may then control the continuously variable metering device to control the proportion of refrigerant circulating via the by-pass channel.

[0035] The temperature control system may not comprise a heater for adding heat to the load. Advantageously, this reduces the overall energy consumption of the temperature control system, as the temperature control system does not need to supply power to a heater. Alternatively, the temperature control system may comprise a heater for adding heat to the load. Advantageously, this may allow the temperature control system to achieve heating in addition to cooling and allow for finer temperature adjustment by using the heater to add small amounts of heat when necessary. The load may comprise a coolant. The load may be a liquid bath or a liquid reservoir. The load may comprise water, propylene glycol, ethylene glycol or glycerol.

[0036] Different applications may need different volumes of load. In many embodiments, the volume of the load may be between 0.5 litres and 150 litres, for example between 1 litre and 100 litres, for example between 5 litres and 50 litres.

[0037] The temperature control system may comprise a pump for circulating the load and / or a stirrer for agitating the load. It may be easier to maintain a precise temperature if the load is circulating, for example in which the load is a stirred water bath.

[0038] According to the present disclosure, a method of controlling the temperature control system may comprise measuring a temperature of the load using a temperature sensor and processing the measured temperature of the load using a controller. The controller is configured to vary the proportion of refrigerant circulating via the by-pass channel. For example, the controller is configured to use the temperature data from the load and vary the proportion of refrigerant circulating via the by-pass channel to control the temperature of the load to a desired temperature. The method may comprise controlling at least one continuously variable metering device using the controller to control with continuous variability the proportion of refrigerant circulating via the by-pass channel.

[0039] Preferred Embodiments of the Invention

[0040] Preferred embodiments of the invention will now be described with reference to the figures, in which:

[0041] Figure 1 is a schematic illustration of a temperature control system according to a first embodiment.

[0042] Figure 2 is a schematic illustration of the temperature control system of Figure 1 , where the temperature control system is coupled to a load.

[0043] Figure 3 is a schematic illustration of the temperature control system of Figure 1 , where the temperature control system is coupled to a load with a secondary circuit.

[0044] Figure 1 illustrates a schematic of a temperature control system 10 according to an embodiment of the present disclosure. The temperature control system 10 comprises a refrigeration system 20 configured to pump a refrigerant around a refrigerant circuit. In this embodiment, the refrigerant is R290. However, in the other embodiments, the refrigerant may be any suitable refrigerant, preferably a suitable non-toxic, non-CFC refrigerant. The refrigerant circuit comprises an evaporator 21 , a compressor 22, a condenser 23 and an expansion device 24. The expansion device 24 may comprise any suitable expansion means, for example the expansion device may comprise, or be, a capillary tube, an orifice plate or an expansion valve.

[0045] The evaporator 21 is fluidically coupled to the compressor 22 by a first refrigerant circuit portion 15. The compressor 22 is fluidically coupled to the condenser 23 by a second refrigerant circuit portion 16. The condenser 23 is fluidically coupled to the expansion device 24 by a third refrigerant circuit portion 17. The expansion device 24 is fluidically coupled to the evaporator 21 by a fourth refrigerant circuit portion 18.

[0046] In use, refrigerant circulates around the refrigeration circuit. The evaporator 21 receives refrigerant in the form of a low pressure, low temperature liquid and vapour mixture from the expansion device 24 via the fourth refrigerant circuit portion. Heat from the environment surrounding the evaporator, which may be a load, is absorbed by the liquid and vapour refrigerant mixture to fully evaporate the mixture such that the refrigerant exits the evaporator as a gas.

[0047] The compressor 22 receives and compresses low pressure, vaporised refrigerant from the evaporator 21 via the first refrigerant circuit portion 15. After compression, the refrigerant is a high pressure, high temperature gas. The compressor 22 also acts as a pump to move the refrigerant around the refrigerant circuit.

[0048] The condenser 23 receives the high pressure, high temperature gas from the compressor 22 via the second refrigerant circuit portion. Heat from the refrigerant is removed to the external environment and the refrigerant condenses to becomes a high pressure, low temperature liquid.

[0049] The expansion device 24 receives the high pressure, low temperature liquid from the condenser 23 via the third refrigerant circuit portion. As the refrigerant expands on passing through the expansion device, it forms the low pressure, low temperature mixture of vapour and liquid that circulates via the evaporator once more.

[0050] In passing around the refrigeration circuit, the refrigerant moves heat from the environment surrounding the evaporator 21 to the environment surrounding the condenser 23. Thus, the evaporator 21 , compressor 22, condenser 23, and expansion device 24 components of the refrigeration system may function as they would in a standard vapour-compression refrigeration system, which is well-understood by the person skilled in the art.

[0051] The refrigerant circuit further comprises a by-pass channel 30 which fluidically connects the second refrigerant circuit portion 16 with the fourth refrigerant circuit portion 18. The by- pass channel 30 allows refrigerant that has been compressed by the compressor 22 to bypass the condenser 23. Thus, the by-pass channel allows high pressure, high temperature gas that has passed through the compressor to mix with the low temperature low pressure vapour and liquid mixture downstream of the expansion device. Any refrigerant that bypasses the condenser does not have its heat removed to the external environment.

[0052] A continuously variable metering device 31 is located in the by-pass channel 30 to control a flow of refrigerant circulating via the by-pass channel 30. By completely closing the continuously variable metering device 31 , the passage of refrigerant via the by-pass channel is prevented. In this circumstance, all of the refrigerant flows through the circuit via the condenser. By actuating the continuously variable metering device 31 , the proportion of refrigerant passing through the by-pass channel 30 can be controlled. The greater the proportion of refrigerant that passes through the by-pass channel, the greater the proportion of refrigerant that does not circulate via the condenser.

[0053] At any point during operation, the temperature control system 10 has a cooling capacity. Cooling capacity is the amount of heat that the evaporator 21 is able to absorb from a load (i.e. remove from the load) while the system is operating. For any specific system conditions, the temperature control system can be said to have a maximum cooling capacity. The maximum cooling capacity is a maximum amount of heat that can be removed from the load under those specific conditions. For example, a temperature control system may have a maximum cooling capacity of 250W for a load temperature of 20 °C; 200W at 0 °C; 100W at -10 °C and 50W at -20 °C. For temperature control systems described herein, the maximum cooling capacity is achieved when the compressor is running continuously and 100% of the refrigerant is flowing through the condenser as it circulates the refrigerant circuit. Thus, at maximum cooling capacity, a maximum amount of heat is absorbed from the load by the evaporator 21 and a maximum amount of heat is dissipated to the external environment by the condenser 23.

[0054] The cooling capacity may be continuously reduced from the maximum cooling capacity by continuously increasing the proportion of refrigerant circulating via the by-pass channel 30. By increasing the proportion of refrigerant circulating via the by-pass channel 30, the temperature of the refrigerant entering the evaporator 21 may be increased as the amount of high temperature gas entering the fourth refrigerant circuit portion 18 from the second refrigerant circuit portion 16 via the by-pass channel 30 is increased. The cooling capacity may be reduced to a minimum cooling capacity when a maximum proportion of refrigerant is circulated via the by-pass channel 30. Thus, at the minimum cooling capacity, a minimum amount of heat is absorbed from the load by the evaporator 21 and a minimum amount of heat is dissipated to the external environment by the condenser 23. The minimum cooling capacity may be, for example, 0W where all of the refrigerant circulates via the by-pass channel 30 and no heat is dissipated by the condenser 23. In certain circumstances the minimum cooling capacity may have a negative value, that is, heat may be supplied to the load. This may happen if more heat is introduced to the refrigerant by the compressor than is removed from the refrigerant as it circulates.

[0055] In this specific embodiment, the continuously variable metering device 31 has a continuously variable orifice size. The orifice size may be continuously adjustable from a fully closed state to fully open state. For example, the continuously variable metering device 31 may be an electronic expansion valve. Thus, in this embodiment the continuously variable metering device 31 may be actuated to continuously vary the proportion of refrigerant circulating via the by-pass channel 30 by continuously adjusting the orifice size of the continuously variable metering device 31 . A maximum proportion of refrigerant may circulate through the continuously variable metering device 31 when the orifice size is in the fully open state.

[0056] The arrows in Figure 1 show the direction in which the refrigerant is to be pumped around the refrigeration system 20. A first return path 25 (shown using double-lined arrows) is defined from a compressor output to an evaporator inlet through the condenser 23 and the expansion device 24. A second return path 35 (shown using dashed arrows) is defined from the compressor output to the evaporator inlet via the by-pass channel 30.

[0057] Figure 2 illustrates a temperature control system 11 comprising the same refrigeration system 20 of Figure 1 when coupled to a load 40. The evaporator 21 is thermally coupled to the load 40 such that the evaporator 21 is able to remove heat from the load 40. The temperature control system 11 further comprises a temperature sensor 51 and a controller 52, in which the temperature sensor 51 , controller 52 and continuously variable metering device 31 are electrically connected (shown using dashed arrows).

[0058] The temperature control system 11 uses the temperature sensor 51 to continuously measure the temperature of the load and feedback the temperature measurements to the controller 52. Continuous control of the temperature control system 11 thus comprises the steps of measuring a temperature of the load using the temperature sensor 51 , processing the measured temperature of the load, and controlling the continuously variable metering device 31 using the controller 52, such that the proportion of refrigerant circulating via the by-pass channel 30 is controlled with continuous variability. For example, the temperature control system of Figure 2 may be used to control a refrigerated circulating bath for controlling the temperature of laboratory samples. For example, the load may be a 5.5 litre water bath used to precisely control the temperature of laboratory samples arranged in thermal communication with the water bath. The temperature control system may be used to control the water bath temperature to a target temperature between 0 °C and 90 °C to with ± 0.05 °C accuracy. The temperature sensor may be placed in the water bath to continuously measure the water bath temperature.

[0059] The temperature control system may need to maintain the water bath temperature at a precise temperature of 10 °C. As laboratory samples are added and removed to the water bath, the water bath temperature may fluctuate in response. The temperature control system may need to increase cooling if a warmer laboratory sample is added to the water bath and the temperature of the load is increased. Conversely, the temperature control system may need to reduce cooling if laboratory samples are removed from the water bath.

[0060] The temperature control system may have a maximum cooling capacity of 400W at a load temperature of 10 °C. In other words, the evaporator may be able to absorb a maximum of 400W heat from the water bath when the target water bath temperature is 10 °C.

[0061] At maximum cooling capacity, the continuously variable metering device is closed, and all the refrigerant circulates along the first return path and no refrigerant circulates via the second return path. In this example, the continuously variable metering device may be an electronic expansion valve with a continuously variable orifice size.

[0062] However, in use the temperature control system may not always need to operate at maximum cooling capacity but may need to continuously adjust its cooling capacity to maintain the temperature of water bath at the required target temperature.

[0063] For example, the temperature control system may initially operate at maximum cooling capacity to reduce the water bath temperature from room temperature, 25 °C, to 10 °C. However, a significantly lower cooling capacity may be required to maintain temperature of the load at 10 °C For example, it may only be required to remove 150W of heat to maintain the load at the target temperature of 10 °C. Thus, when the temperature sensor detects that the water bath temperature is approaching 10 °C, the controller may gradually and continuously reduce the cooling capacity to 150W by continuously increasing the orifice size of electronic expansion valve such that the proportion of refrigerant circulating via the bypass channel continuously increases from 0% to 75%. Thus, the temperature control system is able to continuously reduce its cooling capacity to prevent the water bath from dropping significantly below 10 °C, and to maintain the load temperature at 10 °C with a high level of precision and stability.

[0064] If then, for example, several room temperature laboratory samples are then added to the water bath, the water bath temperature may increase as heat is transferred from the laboratory samples to the water bath. The load volume is also effectively increased with the addition of the laboratory samples. When the temperature sensor detects this increase in temperature, the controller acts to reduce the proportion of refrigerant flowing via the bypass, which temporarily increases the cooling capacity to 300W to counteract the increase in temperature. The controller may, for example, continuously reduce the orifice size of the continuously variable metering device such that the proportion of refrigerant circulating via the by-pass channel continuously decreases to 30%, resulting in more heat being removed from the load.

[0065] When the water bath temperature again decreases to the target temperature of 10 °C, the temperature control system may reduce the cooling capacity to, for example, 152W to maintain the increased load at 10 °C. It is noted that the cooling capacity required to maintain the load at 10 °C may have changed slightly due to the addition of samples into the load.

[0066] Thus, the temperature control system may be able to control the cooling capacity of the refrigerated circulating bath with continuous variability to maintain the water bath temperature at 10 °C. Advantageously, the cooling capacity may be continuously matched to the load requirements without excessive energy consumption or input.

[0067] In a second example, the temperature control system of Figure 2 may be used to control the temperature of a load to various calibration temperature points between -40 °C and 150 °C. The load may comprise, for example, a reservoir of propylene glycol. A temperature measuring device may then be calibrated against the load at the calibration temperature points. Advantageously, the temperature control system may be able to continuously maintain a load temperature to within ± 0.05 °C of a target load temperature. Thus, the calibration temperature points may be accurately controlled.

[0068] Figure 3 illustrates a same temperature control system 12 similar to the temperature control system 11 of Figure 2, except that the load 45 comprises a reservoir 41 , a secondary circuit 44 and a pump 42 for circulating a coolant around a secondary circuit 44. The circulating coolant may absorb heat from an external body 43. The evaporator 21 may then remove the heat from the reservoir 41 and thus control the temperature of the load 45. For example, the temperature control system of Figure 3 may be used in a water cooling unit for cooling a laser, where the laser is the external body to be cooled. As laser crystals generate heat during operation, a laser cooling unit may be required to pump water at 15 °C around the laser crystals to keep the crystals between 20 °C and 30 °C. The secondary circuit may comprise flexible water tubes to be connected to the laser, such that the pump may pump water from the reservoir around the laser crystal. The temperature control system may be able to continuously adjust its cooling capacity as described above to counteract the heating effects of the laser such that the water remains at 15 °C. Advantageously, the water temperature may be adjusted to the target temperature of 15 °C with continuous variability to ensure minimal temperature fluctuations of the laser.

[0069] In another example, a temperature control system may be used to cool solvent vapours created during a distillation process. The temperature control system may be coupled to a plurality of rotary evaporators, in which each rotary evaporator comprises a condenser comprising a coolant for cooling solvent vapours to -10 °C. The coolant may be a glycerol solution with a freezing temperature of -37 °C. The cooling capacity of the temperature control system may need to be continuously controlled to maintain the coolant at a constant temperature of -10 degree Celsius in each rotary evaporator while the amount of vapour to be condensed continuously varies. For example, the cooling capacity may be continuously variable between 50W and 200W. For example, the power input to the temperature control system may be 100W. Advantageously, the temperature control system is able to continuously control the cooling capacity to adjust for some of the plurality of rotary evaporators being off and / or having continuously variable cooling demands.

Claims

Claims:1 . A temperature control system for controlling the temperature of a load, comprising a refrigeration system configured to pump a refrigerant around a refrigerant circuit, the refrigerant circuit including an evaporator couplable to the load, a compressor, a condenser, and an expansion zone downstream of an expansion device, the refrigerant circuit including a by-pass channel allowing refrigerant to by-pass the condenser, in which a cooling capacity of the refrigeration system is controllable with continuous variability by varying the proportion of refrigerant circulating via the by-pass channel.

2. A temperature control system according to claim 1 in which the cooling capacity is controllable between a first cooling capacity and a second cooling capacity, the first cooling capacity being a maximum cooling capacity available when 100% of the refrigerant circulates via the condenser, and the second cooling capacity is less than 20% of the first cooling capacity, for example less than 10%, or 5%, or 2%, or 1% of the first cooling capacity.

3. A temperature control system according to claim 1 or claim 2 in which the proportion of refrigerant circulating via the by-pass channel is variable between 0% and 100%, for example between 0% and 90% , for example between 1% and 90%, for example between 0% and 80% , for example between 1% and 80%.

4. A temperature control system according to any preceding claim in which the proportion of refrigerant circulating via the by-pass channel is controlled by at least one continuously variable metering device.

5. A temperature control system according to claim 4 in which the at least one continuously variable metering device is located in the by-pass channel.

6. A temperature control system according to claim 4 or claim 5 in which a second valve is located in the by-pass channel.

7. A temperature control system according to any preceding claim in which a first return path is defined from a compressor output to an evaporator inlet through the condenser and the expansion device.

8. A temperature control system according to any preceding claim in which a second return path is defined from a compressor output to an evaporator inlet via the by-pass channel.

9. A temperature control system according to any preceding claim in which the temperature control system comprises a temperature sensor for measuring a temperature of the load, for example a PT- 1000 temperature sensor.

10. A temperature control system according to any preceding claim comprising a controller, in which the controller is electrically connected to the temperature sensor and the at least one continuously variable metering device.11 . A temperature control system according to any one of claims 4 to 10 in which the at least one continuously variable metering device is an electronic expansion valve.

12. A temperature control system according to any one of claims 4 to 11 in which the at least one continuously variable metering device has a continuously variable orifice size.

13. A temperature control system according to any preceding claim, in which the expansion device comprises a capillary tube, an orifice plate or an expansion valve, for example a thermostatic expansion valve or an electronic expansion valve.

14. A temperature control system according to any preceding claim, in which the cooling capacity is continuously variable between 0W and 3000W, for example between 0W and 2000W or between 0W and 100W, or between 50W and 400W.

15. A temperature control system according to any preceding claim in which the temperature control system controls the temperature of the load to a target load temperature of between -50 degrees Celsius and 150 degrees Celsius.

16. A temperature control system according to any preceding claim in which the temperature control system controls the temperature of the load to within ± 1 degree Celsius of the target load temperature, preferably to within ± 0.5 degrees Celsius of the target load temperature, preferably to within ± 0.2 degrees Celsius of the target load temperature, preferably to within ± 0.1 degrees Celsius of the target load temperature, preferably to within ± 0.05 degrees Celsius of the target load temperature.

17. A temperature control system according to claim 15 or claim 16 in which the cooling capacity is variable between 150W and 400W when the target load temperature is between 10 degrees Celsius and 30 degrees Celsius.

18. A temperature control system according to any one of claims 15 to 17 in which the cooling capacity is variable between 50W and 200W when the target load temperature is between -20 degrees Celsius and 0 degrees Celsius.

19. A temperature control system according to any preceding claim in which a coefficient of performance of the temperature control system is variable between 0.5 and 4, for example between 1 and 3.5.

20. A temperature control system according to any preceding claim in which the temperature control system does not comprise a heater.21 . A temperature control system according to any one of claims 1 to 19 in which the temperature control system comprises a heater.

22. A temperature control system according to any preceding claim in which the refrigerant is R290.

23. A temperature control system according to any preceding claim in which the load comprises water or propylene glycol.

24. A temperature control system according to any preceding claim in which the volume of the load is between 0.5 litres and 150 litres.

25. A temperature control system according to any preceding claim comprising a pump for circulating the load.

26. A temperature control system according to any preceding claim in which the refrigerant circuit comprises a drier for receiving high pressure liquid from the condenser and removing moisture from the high pressure liquid.

27. A temperature control system according to any preceding claim in which the compressor is configured to operate continuously.

28. A laboratory chiller comprising a temperature control system as defined in any of claims 1 to 27, in which the evaporator is located within a coolant bath such that the evaporator is able to couple with and cool the coolant, for example in which the coolant bath has a volume of between 0.5 litres and 100 litres.

29. A laboratory chiller comprising a temperature control system as defined in any of claims 1 to 27, in which the evaporator is configured to control the temperature of between 0.5 litres and 100 litres of coolant.

30. A spectrophotometer comprising a temperature control system as defined in any of claims 1 to 27, in which the evaporator is configured to control the temperature of a cell of the spectrophotometer.31 . A laser system comprising a temperature control system as defined in any of claims 1 to 27, in which the evaporator is configured to control the temperature of a cooling fluid surrounding an active laser medium, for example surrounding a laser generating crystal.

32. A rotary evaporator comprising a temperature control system as defined in any of claims 1 to 27.

33. A method of controlling a temperature control system according to any preceding claim comprising the steps of measuring a temperature of a load, and varying the proportion of refrigerant circulating via the by-pass channel with reference to the temperature of the load in order to vary the cooling capacity of the refrigeration system and control the temperature of the load.

34. A method according to claim 33 in which the temperature of the load is measured continuously, for example in real time.

35. A method according to claim 33 or 34 in which the proportion of refrigerant circulating via the by-pass channel is varied in real time in response to variations in temperature of the load.

36. A method according to any of claims 33 to 35 in which the temperature control system comprises a controller, and in which the controller monitors signals indicating temperature of the load and actuates at least one continuously variable metering device to control with continuous variability the proportion of refrigerant circulating via the by-pass channel.

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