Icing control with accessories for increasing the efficiency of heat exchangers: Hardware and software for increasing efficiency through controlled icing in heat transfer processes in air conditioning and ventilation systems.

Abstract

Systems consisting of hardware and software for increasing efficiency through controlled icing in heat transfer processes in air conditioning and ventilation systems, for example in controlled residential ventilation systems with heat recovery or similar process systems such as evaporator units in refrigeration or heat pump systems.

Description

Hardware and software for increasing efficiency through controlled icing in heat transfer processes in air conditioning and ventilation systems, for example in controlled residential ventilation systems with heat recovery or similar process systems such as evaporator units in refrigeration or heat pump systems. Patent claim or utility model claim

[0001] The patent application seeks protection for control loop systems to be developed to increase the annual heat transfer rate, using heat recovery in controlled residential ventilation systems as an example. The aim is to improve simple, controlled icing prevention using preheaters with electric resistance heating, hot water heating, or similar systems, controlled solely by the temperature signal. This includes systems with controlled defrosting devices, such as evaporator units in heat pump systems or similar control systems.

[0002] Increases in resistance due to icing from the condensate formed when humid air is cooled in ventilation and air conditioning systems, both in terms of the heat transmission resistance through the heat exchanger wall and the increase in resistance and thus the increase in pressure loss in the heat exchanger channels for the heat transfer media, should be referenced and integrated into control loops via pressure or differential pressure as a controlled variable and operated optimally to maximize energy efficiency and cost-effectiveness. In addition to the differential pressure at the recuperation heat exchanger as a controlled variable, the heat output, automatically recorded in a suitable manner, should be included as a control variable, as should the outside air temperature for a plausibility check. If no measurable increase in resistance occurs in the piping system on the heat-supplying side, e.g. because the evaporator is installed outdoors, the heat output measured at a suitable location should be used as the reference variable.

[0003] Commercially available and customary heat exchangers – colloquially called "heat exchangers" – e.g., made of plastic or metal, adapted in design and equipment and incorporated into compact ventilation systems are included, as are resulting derivations and applications to related processes such as split systems for heat recovery or evaporators in refrigeration or heat pump systems, all technical heat transfer processes in which condensate is produced from air or other gas and can form a layer of ice that influences the heat transfer resistance of the heat exchanger, as well as underwater systems such as heat exchanger tube bundles in ice storage systems or similar.

[0004] Existing ventilation and air conditioning systems demonstrate technical solutions using temperature measurements as a signal for controlled ice prevention.

[0005] A prerequisite for the formation of water ice is temperatures below freezing (0°C), with negligible dependence on ambient pressure. The amount of ice formed per unit time, and thus the rate of ice layer growth, depends on the moisture content and temperature of the media flows on both sides of the heat exchanger wall—in the example, the outside and exhaust air flows—and the design of the exchanger. The transferred heat output is determined by the transfer area, heat transfer coefficient, and temperature difference between the primary and secondary sides of the heat exchanger, as well as the primary and secondary heat transfer medium flows with corresponding heat capacity and temperature difference. The heat transfer coefficient refers to flow changes due to changes in heat transfer, as well as changes in layer thickness due to ice formation (or contamination).Increased resistance in the flow channels on either side of the heat exchanger wall leads to reduced flow unless compensated for by increasing the speed of the conveying flow or positive displacement machine. The recovered heat relative to the theoretically maximum possible heat recovery yields a corresponding heat recovery coefficient. By measuring the pressure loss—the differential pressure—across the path through the heat exchanger, including possible condensate formation and the corresponding probability of icing, the quality and quantity of ice formation can be managed using differential pressure as a control variable: A growing layer of ice increases the flow resistance, reduces the heat transfer coefficient, and results in a correspondingly higher pressure drop or pressure loss.Similar to the contamination level measurement of air filters in ventilation systems to generate a maintenance message, the degree of icing, measured via the differential pressure, should serve as a reference value and control variable.

[0006] Equipped with modular, replaceable and expandable components for retrofitting or new production, integrated into the control system of the ventilation system or heat exchanger, the aim is to increase efficiency by increasing the transferable recuperation heat. The features of the additional parts and systems include the greatest possible utilization of self-regulating effects and minimize increased investment, operation, and maintenance costs, while further optimizing procedures and processes as well as manageability, user-friendliness, and safety, while focusing on the core function of the system.

[0007] The innovation lies in the integration of additional components for new equipment or retrofitting to established heat exchanger systems, for the purpose of energy-optimized icing control of condensate at operating temperatures below freezing point.

[0008] For plate heat exchangers in compact ventilation systems or other applications, e.g., closed-loop heat exchangers, rotary heat exchangers, switching storage tanks, heat pumps, etc.

[0009] The concrete sketchy initial approach in the drawing for this submission shows a controlled residential ventilation system. List of reference symbols 1 Heat-emitting air stream with condensable water vapor content 2 heat exchangers with temperatures below the dew point to (1) 3 Pressure sensor and signal generator 4 Fan to convey the heat-absorbing air 5 differential pressure sensors 6 controls 7 Control signal line to fans 8 Pressure chamber for heat-absorbing air flow 9 condensate drains 10 Fan to promote the heat-emitting air 11 Air preheater 12 Temperature sensor and signal generator 13 controllers 14 Circulation pump 15 water heat storage tanks 16 heat exchangers 17 Temperature sensor and signal transmitter for water heat storage 18 Temperature sensor and signal transmitter for outside air temperature Existing heat exchangers • Design and execution ◯ made of metal, ceramic, plastic or composite materials ◯ as tube bundles or similar ◯ as plate heat exchanger with capillaries • Plates soldered or welded • Plates with seals and force-locking connection • Operating modes ◯ in direct current ◯ in countercurrent ◯ in cross-current • Energy supply ◯ as needed from heat or cold generation for heat supply or consumption ◯ Pressure losses due to media flows balanced from gravity and pumps, fans or compressors • Placement ◯ In the annex • Central • In the periphery ◯ Inside or outside the building ◯ Inside the thermal building envelope or outside • Increased efficiency ◯ by recording and introducing energy flows into control loops ◯ by making full use of unnecessary, energy-relevant safety distances, particularly with regard to ice formation, as long as no harmful effects can occur Heat exchanger with icing control • Design and construction, drive types, etc. such as existing heat exchangers improvements through innovations as stated in the protection objectives. • Operating modes ◯ as introduced and proven, preferably automatically ◯ extended by control loops for recording and controlling as close as possible to the actual energy flows ◯ visionary seen by means of AI-guided and optimized control loops with algorithms for heat balancing and efficiency improvement • Goals ◯ Increase in recovered heat energy through control loop-controlled approach to the maximum achievable icing limit in the comfort range without disturbance • Self-regulating effect: Due to the formation of ice layers on the heat exchanger walls, the free flow cross-section is narrowed, the flow velocity increases and thus also the heat transfer coefficient • Varying the ratio of the heat transfer medium flows on both sides of the heat exchanger wall so that the transferred heat does not allow the ice layer to grow any further and this operating state can be maintained at the limit, tending towards the end of the process cycle so that the ice layer is melted again • If it cannot be expected that the ice layer can be melted or maintained at a maximum beneficial layer thickness during controlled continuous operation, the system should first be switched off in order to exploit storage effects • If no storage effects can be exploited, a melting routine should be activated, a process known from heat pump or refrigeration systems uses a cycle reversal, the evaporator becomes the condenser and vice versa, in the case of KWL systems, by operating the system as a pure exhaust air system • Continued operation of the system as delayed as possible (energy or air quality still in the beneficial range) until the heat exchanger does not freeze again immediately • If delayed restart is not possible, start up from the minimum necessary ratio of cold heat transfer medium to heat-generating air • After the start of the regular operation, this takes place cyclically until the end of the demand under automatically resulting repeating cycles of the icing and de-icing control • The above verbally outlined control system is optimized and monitored with regard to the maximum possible energy yield in an economical and demand-oriented manner, limited by necessary safety measures ◯ Exergy reservation - e.g. of electrical energy from PV systems - for higher-value tasks by avoiding frost protection through electrical resistance heating ◯ If suitable heat storage systems with sufficient capacity and the potential to deliver temperatures above the freezing point of water are available, these should be integrated if necessary in order to optimise the regular operation, to reduce or avoid the number of operationally problematic defrosting cycles and to increase the capacity of the heat storage system, e.g. a hot water storage tank, by cooling it down as close as possible to 0°C in the cold area, in order to also increase the energy gain of any solar thermal or heat pump system by reducing the temperature of the heat sink and thus increasing the excess temperature at the corresponding heat exchangers there. ◯ When implementing complete systems (1) to (18), the subsystem (1) to (10) has energetic advantages without preheating by the system (11) to (18) and would therefore have to be operated with priority in a subsequent control system, unless special circumstances and conditions require otherwise. ◯ If subsystems (11) to (17) are present and correspondence with (18) is possible, the outside air (18) should be cooled in an energetically optimized manner for the "summer operating case", the comfort of the ventilation system should be increased and useful heat energy should be introduced into the water heat storage if the corresponding operating conditions are given. ◯ Function and efficiency control by recording and incorporating energy flows to optimize regular operation

Claims

[1] Systems consisting of hardware and software to increase efficiency through controlled icing in heat transfer processes in air conditioning and ventilation systems, for example in controlled residential ventilation systems with heat recovery or similar process systems such as evaporator units in refrigeration or heat pump systems. [2] Systems for controlled icing in heat transfer processes according to 1., characterized by that through system-integrated control loop or control loops with controlled variable as close as possible to the formation of ice layer, as a discrete control loop or system of control loops retrofittable in existing systems or integrated in new systems. [3] Systems for controlled icing according to 1. and 2., characterized by that the section to be iced is monitored and controlled by means of pressure sensors and transmitters (3), the controlled variable is formed as a reference value for the icing condition from the differential pressure and is signaled to a transmitter system (5). [4] Controlled icing systems according to 1. to 3., characterized by that a dynamic control variable (7) is formed from the actual value of the controlled variable differential pressure via a discrete controller or digital, programmable control and regulation system, for the purpose of controlling the fans (4) and (10) in such a way that the ice-forming heat flow is changed. [5] Controlled icing systems according to 1. to 4., characterized by that system (11) to (18) is put into regular operation when 4. is exhausted. [6] Controlled icing systems according to 1 to 5, characterized by that the control loops correspond with each other and are optimized by artificial intelligence. [7] Controlled icing systems according to 1 to 6. characterized by that in addition to the differential pressure (5) the operating point change of the fan (10) is referenced and implemented as a control or control variable. [8] Controlled icing systems according to 1 to 7. characterized by that, as an alternative to the differential pressure (5), e.g. in the case of evaporator icing in heat pumps or refrigeration machines, the operating point change of the compressor is implemented as a control and monitoring variable. [9] Controlled icing systems according to 1 to 8. characterized by that commercially available components and elements are used as far as possible and that the additional components are essentially developed and integrated or the production of new devices is modified accordingly. [10] Controlled icing systems according to 1 to 9. characterized by that after the development and prototype success, appropriate variants of use are developed, modified, documented, published and brought to market readiness and finally onto the market.

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