EP2775234A2

EP2775234A2 - Water source heat pump and the optimization method of the heat pump operation

Info

Publication number: EP2775234A2
Application number: EP13461550.9A
Authority: EP
Inventors: Boguslaw Zakrzewski; Wojciech Tuchowski
Original assignee: Zachodniopomorski Uniwersytet Technologiczny w Szczecinie
Current assignee: Zachodniopomorski Uniwersytet Technologiczny w Szczecinie
Priority date: 2013-03-07
Filing date: 2013-10-02
Publication date: 2014-09-10
Also published as: PL219940B1; PL403038A1

Abstract

The water source heat pump according to the invention containing lower heat source (3), which at a low water temperature is powered by heat energy originating from the water phase transition between the liquid state and the solid state, the upper heat source (2), connected in the counter-clockwise thermodynamic cycle, is equipped with adjustment and control system, an expansion element (5), water source (11), is characterized by the fact that the lower heat source (3) has a circulation system of the intermediate fluid containing at least three coils (A) immersed in water, with the intermediary fluid running through and receiving heat from water.

Description

The subject of the invention is a water source heat pump and the optimization method of its operation. The heat pump may be used in system handling individual air conditioners, heating system of single-family houses possessing either a water reservoir or a place where a water reservoir might be located, or there exists a different source of water.
Known from literature, "Kompendium ogrzewnictwa i klimatyzacji" [Compendium of Heating and Air Conditioning] by Rekcnagel, Sprenger and Schramek, issued by OMNI SCALA, Wroclaw 08/09 and presented on a diagram on page 596, the water source heat pump, which is air- powered in t he lower heat source, may also be powered by water, containing an external air cooling system consisting of a compressor connected through pipeline with two heat exchangers, an evaporator and a condenser, equipped with a throttling element and a valve controlling the operation in heating and defrosting cycles. The said publication also presents, on page 2051, a diagram of a heat pump powered from well with groundwater consisting of pipelines of the heat exchanger , a reversing valve, and groundwater pumps. The groundwater is drawn from a supply well and transferred to an evaporator of a heat pump. In that place the heat absorbed in the heat pump is received, and the cooled water is transferred to the drain well. In well-known heat pumps, heat exchangers, for the purpose of increasing the area of heat exchange, are usually equipped with ribbing. Heat pumps which apply water for powering the lower heat source are used where the water temperature is relatively high, that is, where there occurs the so called waste heat: of geothermal waters, discharge waters of power station, sewage etc. In the previously used heat pumps, the lower heat source is powered by heat from water temperature differences.
The patent description PL 209839 presents a water source heat pump and the optimization method of its operation. The water source heat pump containing a lower heat source, upper heat source, connected in a counter- clockwise thermodynamic cycle, equipped with an adjustment and control system and a device for reversing the refrigerant cycle, an expansion element, water source, is characterized by the fact that the lower heat source has two exchangers: an evaporator and a cooler working alternately so that the evaporator operates as a cooler and a cooler operates as an evaporator. The operating method of the heat pump according to the invention is the following: the lower heat source is powered by heat energy from the water phase transition between the liquid state and solid state. The optimization method of the operation of a water source heat pump, where the reversing of the cycle of a refrigerant is applied, is characterized by the fact that the lower heat source is powered by heat energy from the water phase transition between the liquid state and solid state. The refrigerant is directed through the cooler to the evaporator until a layer of ice no bigger than 5mm is created on the evaporator. Upon the icing of the evaporator, the cycle of the refrigerant is reversed so that the evaporator functions as a cooler and the cooler functions as an evaporator. The "cold" accumulated in the cooler, contained in the mass temperature differences, in the heat of ice melting , serves for cooling the liquid medium in the cycle. The function of the exchangers of the lower heat source is changed not earlier than upon defrosting of the cooler. The procedure is followed alternately, when one exchanger is iced on the other exchanger, through the heat delivered by a condensed refrigerant, the ice melts and goes off the surface of the exchanger.
It turned out unexpectedly that the operation of the water source heat pump might be realized more beneficially.
The water source heat pump according to the invention, containing a lower heat source which , at a low water temperature, is powered by heat energy from the water phase transition between the liquid state and the solid state, upper heat source, connected in the counter-clockwise thermodynamic cycle, equipped with adjustment and control systems, an expansion element, water source, is characterized by the fact that the lower heat source has a circulation system of an intermediate fluid, containing at least three coils immersed in water with intermediate fluid running through the coils and receiving heat from water. The circulation system of intermediate fluid contains an electronically controlled intermediate fluid separator, a cooler pipe and an intermediate fluid pump, through which coils are connected to the lower heat exchanger. The intermediate fluid is an antifreeze fluid - a solution of glycol and brine. The coils are made of plastic that is resistant to the temperature and substances contained in water. The coils are placed at different depth of the water reservoir, while during the period of low external temperatures, the coils are placed by the bottom of the reservoir, and when the surface water temperature is above 4°C, the coils are placed under its surface. The operation of the pump according to the invention is based on a periodic change of the number and sequence of the working coils, through which runs an antifreeze intermediate fluid. The coils are heat exchanger immersed in winter. Upon icing of one coil, or few of them, the subsequent one is used for receiving heat from water until a layer of ice is formed on the coil. The previously iced coil is gradually being defrosted; it is switched off - no intermediate fluid flow at that time. In this way, one coil is being covered with ice while the second one and the subsequent ones are being defrosted by the heat of the ambient water and the buoyant force, the remains of ice are being torn off the coil surface (exchanger) and the ice automatically rises to the surface.
The optimization method of water source heat pump operation, according to the invention where cyclical circulation changes of the refrigerant by heat exchanger are applied to power the evaporator of the heat pump cycle, while during the period of low external temperatures, the heat energy from the water phase transition between the liquid state and the solid state on the exchanger surface is used to power the lower heat source, is characterized by the fact that water temperature is measured in the middle of the height of each coil and, through an electronic fluid separator, the intermediate fluid is directed to the coil which, at a given moment, is placed in the water layer of the highest temperature. The intermediate fluid receives the heat of water solidification, next it is directed to the evaporator, where it gives up the heat until an ice layer not bigger than 15mm is formed on the coil. The procedure is carried out for the subsequent coils, while at that time, the iced coil is being gradually defrosted and it may re-power the evaporator of the lower heat source. Depending on the amounts of peak demand for heat, the volume of the heat container is selected - at the side of the heat carrier - in such a way that its volume 10% bigger than the sum of the volume of the operating coils, so as to minimize the number of starts the compressor, to the maximum of 3 - 4 per hour.
The advantage of the solution according to the invention is the use of significant heat resources of the water phase transition between the liquid state and the solid state (solidification), low costs of coil exchanger (PVC) and high resistance to salinity condition etc. in sea water or water containing large amounts of chemical compounds. The solution allows for flexible movement of coils under the water surface or by the bottom depending on the water temperature, at high water temperature in the surface layer, while in winter conditions - at the bottom layer. The heat pump possesses high COP independent of the external air temperature (especially significant in the periods of low external temperatures). The proposed solution allows for almost virtually continuous operation of the heat pump. The periods of changeover of the exchangers of intermediate fluid have no significance in the heat powering of the upper heat source. The proposed invention also eliminates typical drawbacks of water source and air source heat pumps, especially when the ambient temperatures in a given region fall below 0°C it guarantees high and stable thermal supply power. It practically eliminates the break for the evaporator defrosting time and eliminates the characteristic adverse cooling of the room during the defrosting period. Besides, it allows for significant increase in efficiency of the heat pump in two ways: by increasing the evaporation temperature and pressure, and eliminating the power used for the defrosting process in the functioning of the air source heat pump. The solution, according to the invention, greatly reduces the energy consumption by the heat pump, increasing its efficiency in external conditions where the ambient temperature is close to 0°C or below 0°C.
The solution according to the invention is presented in the performance examples and on the drawing, where fig.1 presents a diagram of a water source heat pump heating up the air, fig.2 presents a diagram of a reversible water source heat pump heating up the air, fig.3 presents a diagram of a reversible water source heat pump cooling the air.

Example I

The water source heat pump contains lower heat source 3, which at a low water temperature is powered by heat energy from water phase transition between the liquid state and the solid state, upper heat source 2, connected in the counter-clockwise thermodynamic cycle equipped whit adjustment and control system, expansion element 5, water source 11, circulation system of intermediate fluid. Lower heat source - evaporator/heat container 3 is connected to A₁, A₂, A₃, A₄ coils and an air condenser/heater 2, between which an expansion element is placed in the form of an expansion valve 5.
A₁, A₂, A₃, A₄ coils are placed in a water reservoir 11 constituting an external heat container. A glycol solution runs through to the coils, receiving heat from water. The evaporator/heat container 3 is connected to a regenerative exchanger 4, compressor 1 and condenser 2. The air/condenser heater 2 is connected to the other side through the regenerative exchanger/ steam drier 4 and filer 10 with an expansion valve 5. The operation of the water source heat pump is controlled by a control system though an electronic controller 12. The refrigerant from the condenser 2, through the expansion valve 5, is directed to the evaporator/heat container 3, where its expansion takes place and where it change its state of aggregation, receiving heat from the glycol solution running through the A₁, A₂, A₃, A₄ coils immersed in reservoir 11. The glycol solution that gives up the heat is cooled in the evaporator/heat containers 3 below 0°C and running through the coils, which at a given moment are placed in the water layer of the highest temperature, the glycol solution receivers heat from water, the water freezes on the coil surface at the water temperature of around 4oC and below, creating an ice layer. The number of coils with the glycol solution running through depends on the heat load, though it is always maximum half of the coils connected to the evaporator/heat containers 3. The gas refrigerant is sucked in by the compressor 1, which directs it to the condenser 2, where it gives up the heat of condensation. The circulation system of the intermediate fluid consist of four coils: A₁, A₂, A₃, A₄, an electronic fluid separator 7, a collector pipe 9 and an intermediate fluid pump 6. The system is connected to the evaporator/heat container 3. The A₁, A₂, A₃, A₄ are made of plastic resistant to temperature and aggressive substances contained in water . The A₁, A₂, A₃, A₄ coils, functioning as heat exchanger, are placed at different depths of water reservoir. Depending on the water temperature, which is measured in the middle of the height of each coil, the electronic fluid separator 7, through electronic valves 8, directs the intermediate fluid to the proper coil. During the period of low external temperatures, during the operation of the water source heat pump, the glycol solution from the coil/s is directed to the evaporator 3 where it gives up the heat up to the moment where on the A1 coil a layer of ice not bigger than 15 mm is formed, next the glycol solution is directed to the subsequent coil so that the time the iced coil is circulation system of the intermediate fluid.

Example II

The water source heat pump, presented on fig. 2 contains a lower heat source with two interconnected exchangers: an evaporator/heat container 3 connected to three coils A₁, A₂, A₃, and an air condenser/heater 2, between which an expansion element is placed in the form of an expansion valve 5. The A₁, A₂, A₃, coils are placed in a water reservoir 11 constituting a heat container, the brine that runs through the coils receives heat from water. The evaporator/heat container 3, through the four-way valve 13 is connected to the steam drier 4 and an expansion valve 5, and through the four- way valve 14 to the compressor 1. The condenser 2, at the other side, is connected through the four-way valve 14 to the compressor 1.
The heat pump operation in controlled by a control system through an electronic controller 12. The refrigerant from the condenser, through the four-way valve 13, is directed to the steam drier/regenerative exchanger 4, where it is cooled. Further, the refrigerant is directed through filter 10 and an expansion valve 5 and a four-way valve 13 to the evaporator/heat container 3, where it change it state of aggregation receiving heat from the brine. The cooled brine flows to the water reservoir 11, where it is heated up. The water which gives up the heat of solidification freezes on the coil surface which, at a given moment, is placed in the water layer of the highest temperature. The gas medium flows from the evaporator/heat container 3 through the four-way valve 14 and steam drier/regenerative exchanger 4 to the compressor 1 which pumps it to the condenser 2, where it gives up the heat of condensation. Depending on the water temperature, which is measured in the middle of the height of each coil, the electronic fluid separator 7, through electronic valves 8, directs the intermediate fluid to a proper coil. During the period of low external temperatures, during the operation of the water source heat pump, the brine from the coil is directed to the evaporator 3 where it gives up the heat up to the moment where on the A1 coil a layer of ice not bigger than 15mm is created, next the brine is directed to the subsequent coil so that the subsequent coil becomes covered with ice, receiving heat during the ice creation, and at that time the iced coil is gradually defrosted. Upon defrosting, the coil again functions as a heat exchanger in the circulation system of the intermediate fluid. The number of coils with the brine running through depends on the heat load.

Example III

The water source heat pump presented on fig. 3 as in the case presented in example no. 2, with the difference that the controller 12 switches off the compressor 1 and by changing over the four- way valve 13 and 14, it reverses the cycle of the refrigerant. Such a situation occurs during the summer season when one wants to cool air in an evaporator 2, which within the function of heating up the air, works as a condenser.

Claims

The water source heat pump containing lower heat source, which at a low water temperature is powered by heat energy originating from the water phase transition between the liquid state and the solid state, the upper heat source, connected in the counter-clockwise thermodynamic cycle, is equipped with adjustment and control system, an expansion element, water source, is characterized by the fact that the lower heat source (3) has a circulation system of the intermediate fluid containing at least three coils (A) immersed in water, with the intermediary fluid running through and receiving heat from water.
The water source heat pump according to claim 1, characterized by the fact that the circulation system of the intermediate fluid contains an electronically controlled intermediate fluid separator (7), a collector pipe (9) and an intermediate fluid pump (6), through which coils are connected (A) to the lower heat exchanger (3)
The water source heat pump according to claim 1 is characterized by the fact that the intermediate fluid is an anti-freeze fluid - glycol solution or brine
The water source heat pump according to claim 1 is characterized by the fact that the coils are made of plastic resistant to temperature and substances contained in water.
The water source heat pump according to claim 1 is characterized by the fact that the coils (A) are placed at different depths of water reservoir (11), while during the period of low external temperatures, they are placed by bottom of the reservoir, and when the water temperature at the surface is above 4°C, the coils are placed its surface.
The optimization method of the operation of water source heat pump, where the cyclical changes of the refrigerant circulation through heat exchangers are used to power the evaporator of the heat pump cycle, while during the period of low external temperatures the heat energy from the water phase transition between the liquid state and the solid state at the surface of the heat exchanger is used for powering the lower heat source, is characterized by the fact that the water temperature is measured in the middle of the height of each coil and, through an electronic fluid separator, the intermediate fluid is directed to the coil which, at a given moment, is placed in the water layer of the highest temperature, where intermediate fluid receives heat of water solidification, next it is directed to the evaporator where it gives up the heat until the moment when a layer of ice no bigger 15 mm is formed on the coil, and the procedure is repeated for the subsequent coils, during which the iced coil is gradually defrosted and may re-power the evaporator of the lower heat source.
The optimization method according to claim 6 is characterized by the fact, depending on the amounts of peak demand for heat, the volume of the heat container (3) is selected - at the side of the heat carrier - in such a way that its volume 10% bigger than the sum of the volume of the operating coils, so as to minimize the number of starts the compressor, to the maximum of 3 - 4 per hour.