JP4255416B2 - CO2 water heater and its non-frost operation method - Google Patents

Description

The present invention relates to a compressor that compresses a CO ₂ refrigerant on a CO ₂ refrigerant circulation line, a gas cooler that cools a gaseous refrigerant that has been compressed by the compressor to a high temperature and a high pressure, and CO ₂ that is cooled by the gas cooler . A heat pump cycle is configured by sequentially interposing a capillary tube part that decompresses the refrigerant and an evaporator that evaporates the CO ₂ refrigerant that has been decompressed and reduced in temperature by the capillary tube part , and the gas cooler is supplied from the water supply line A water heater that heats the supplied water by exchanging heat between the water and the CO ₂ refrigerant, and the evaporator is an air heat collection type heat exchanger that exchanges heat with outside air to evaporate the CO ₂ refrigerant. The present invention relates to a CO ₂ hot water supply device and a non-frost operation method in the cold season of the hot water supply device .

  In the conventional heat pump type water heater, when the evaporator is an air heat collection type heat exchanger, frost is formed on the air side heat transfer surface of the air heat collection type heat exchanger in the cold season or it is frozen. Or, there is a problem that the ability is reduced.

  As a countermeasure, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2003-222391) includes a defrost circuit for supplying hot gas from a compressor to an air heat recovery heat exchanger, and a water circulation pump for a hot water storage tank. The defrosting operation in which hot gas is supplied to the air heat collection type heat exchanger is made possible in a state in which the water circulation pump is stopped. When the defrosting operation is started and continued for a predetermined time or more, the water circulation pump is driven.

JP 2003-222391 A

  However, in the defrost operation disclosed in Patent Document 1, it is necessary to add a defrost circuit for supplying hot gas from the compressor to the air heat collecting heat exchanger and a control device for executing the defrost operation. However, there is a problem that the device itself is complicated and expensive.

  Therefore, in view of the problems of the prior art, the present invention provides an air collecting heat exchanger that collects heat from outside air, and the air-side heat transfer surface of the air collecting heat exchanger can be used even in the cold season. An object of the present invention is to provide a non-frost operation method capable of preventing frost formation and freezing at low cost and effectively without complicating the apparatus.

Therefore, in order to solve such problems, the present invention is a compressor that compresses the CO ₂ refrigerant on the CO ₂ refrigerant circulation line, and a gas cooler that cools the gaseous refrigerant compressed to the high temperature and high pressure by the compressor. A heat pump cycle is configured by sequentially interposing a capillary tube part for decompressing the CO ₂ refrigerant cooled by the gas cooler and an evaporator for evaporating the CO ₂ refrigerant depressurized by the capillary tube part and becoming a low temperature. the gas cooler is with said CO ₂ refrigerant and the water supplied from the water supply line a water heater for heating the該供feedwater by heat exchange, also the evaporator evaporation the CO ₂ refrigerant and outdoor air heat exchanger In the CO ₂ hot water supply device that is an air heat collection type heat exchanger
The flow rate of the supply water supplied to the gas cooler can be adjusted based on the measured value of the outside air temperature, and a buffer tank is provided by branching a refrigerant circulation line between the outlet side of the gas cooler and the inlet side of the capillary tube, The buffer tank accepts and returns the CO ₂ refrigerant in accordance with the load of the air heat collection heat exchanger .
The present invention also provides a method for non-frost operation of the CO ₂ hot water supply device ,
When the measured value of the outside air temperature becomes low, the flow rate of the water supplied to the gas cooler is reduced to increase the gas cooler outlet temperature, and the refrigerant circulation line between the outlet side of the gas cooler and the inlet side of the capillary tube is branched. A buffer tank is provided, and the buffer tank receives and returns the CO ₂ refrigerant in response to the load of the air heat collection heat exchanger .

In the CO ₂ hot water supply apparatus having the above-described configuration, the amount of heat Qa collected from the outside air (air) in the air heat collection type heat exchanger that exchanges heat with the outside air to evaporate the CO ₂ refrigerant is obtained by the following equation.
Qa = (Ti−To) G × h
However, Ti: inlet air temperature, To: outlet air temperature, G: air volume, h: air enthalpy coefficient The amount of heat collected from the air is the same as the amount of heat collected from the CO ₂ refrigerant. By reducing the supply amount of water to the water heater the gas cooler is provided, the temperature of the outlet side CO ₂ refrigerant in the same gas cooler is increased, adopts heat of CO ₂ refrigerant is reduced.

For this reason, the amount of heat collected from the air is reduced, and thereby the air outlet temperature To rises. By increasing the air outlet temperature To, the air in contact with the air-side heat transfer surface of the air heat collecting heat exchanger is set to the dew point temperature or more to prevent frost formation and freezing.
As the CO ₂ water heater of the structure to which the present invention method is applied, when the load of the evaporator is a heat pump cycle that varies, upon driving the cold season, to detect the outside air temperature, the weather By reducing the amount of water supplied to the water heater based on the state, a decrease in the evaporator outlet temperature can be prevented and non-frost operation can be performed.
The present invention can also be applied to a supercritical CO ₂ refrigeration cycle.

As the decompressor of the CO ₂ water heater of the structure to which the present invention method is applied, key Yapirarichubu can be used.
In order to obtain the length of the capillary tube, first, the pressure / temperature, mass flow rate, and capillary tube inner diameter on the high pressure side, that is, the capillary tube inlet side are given, and the length that can be expanded to the set saturation pressure is calculated. Specifically, the pressure loss of each control volume is given in advance, the control volume length required to obtain the pressure loss is calculated, and added to obtain the length of the capillary tube.

Also preferably, in the case of a heat pump cycle in which the load on the evaporator fluctuates, as in a CO ₂ hot water supply apparatus to which the method of the present invention is applied, a capillary tube parallel structure in which a plurality of capillary tubes are arranged in parallel And an opening / closing valve is provided on the upstream side of each of the plurality of capillary tubes, and the opening / closing control of the opening / closing valve is performed according to the load of the evaporator.
In this case, it is necessary to open at least one on-off valve provided in the capillary tube so as not to block the flow of the CO ₂ refrigerant circulation line when the operation is stopped .
The reason for not providing an on-off valve in one capillary tube is to prevent the refrigerant flow in the CO ₂ refrigerant circulation line from being interrupted when the operation is stopped.
In addition, a buffer tank is provided by branching a refrigerant circulation line between the outlet side of the gas cooler and the inlet side of the capillary tube, and when the load of the air heat recovery heat exchanger is small in the buffer tank, excess CO ₂ refrigerant is supplied. Once with receiving accommodate ceased operation of the heat pump cycle, the CO ₂ accumulated in the buffer tank 6 back to the CO ₂ refrigerant circulation line of the heat pump cycle, the branch pipe provided on the outlet side refrigerant circulation line of the gas cooler, the A buffer tank is provided in the branch pipe with a relief valve interposed, and a return pipe for returning the refrigerant from the buffer tank to the circulation line is provided with an open / close valve.

In the case of a heat pump cycle in which the cooling load of the evaporator fluctuates, it is not possible to deal with all by one capillary tube, and one or more that can cope with the fluctuating load by opening and closing the on-off valve. A capillary tube is selected and a decompression operation is performed.
When the evaporator load is small, the CO ₂ refrigerant becomes excessive. That is, when the amount of water supplied to the gas cooler is decreased, the temperature of the CO ₂ refrigerant on the gas cooler outlet side increases, and the amount of heat collected by the CO ₂ refrigerant (the dryness of the inflow CO ₂ refrigerant increases in the gas cooler ) decreases. As the dryness of the inflow CO ₂ refrigerant in the gas cooler increases, the amount of CO ₂ refrigerant on the low pressure side decreases. As a result, the amount of CO ₂ refrigerant held on the high pressure side increases, and the pressure on the high pressure side increases.

Thus, when the pressure of the CO ₂ refrigerant exceeds a certain value, the branch pipe, the buffer tank, and the return pipe are provided, and a relief valve is provided in the buffer tank so as to allow excess CO ₂ to escape through the relief valve. Set. Thereafter, when the load on the evaporator increases and the CO ₂ becomes insufficient, the opening / closing valve is opened, and the operation of returning the CO ₂ in the buffer tank to the heat pump cycle side is performed.

According to the present invention, a compressor for compressing a CO ₂ refrigerant is CO ₂ refrigerant circulation line on, is compressed in the compressor gas cooler for cooling the gaseous refrigerant to a high temperature and high pressure, is cooled in the same gas cooler capillary tube unit for reducing the pressure of CO ₂ refrigerant, and an evaporator for evaporating the CO ₂ refrigerant is depressurized by CO ₂ refrigerant and the outside air heat exchange with a low temperature at the same capillary tube portion, sequentially interposed configuration A water heater that heats the feed water by exchanging heat between the feed water from the feed water line and the CO ₂ refrigerant in the gas cooler, and prevents a decrease in the outlet temperature of the evaporator. In the non-frost operation method of the CO ₂ hot water supply device that enables frost operation,
When the measured value of the outside air temperature becomes low in the cold season, the flow rate of the supply water supplied to the gas cooler is reduced, the gas cooler outlet temperature is raised, the amount of water supplied to the water heater is decreased, and the gas cooler The refrigerant circulation line between the outlet side and the capillary tube inlet side is branched to provide a buffer tank, and the buffer tank receives and returns the CO ₂ refrigerant in accordance with the load of the air heat collection heat exchanger ( When the load of the air heat collection type heat exchanger is small, the excess CO ₂ refrigerant is accepted, and when the operation of the heat pump cycle is stopped, the CO ₂ accumulated in the buffer tank 6 is transferred to the CO ₂ refrigerant circulation line of the heat pump cycle. (Returning) makes it possible to operate sensitively to the temperature of the outside air, so that reliable non-frost operation is possible. Furthermore, it is not accompanied by an extra device, is inexpensive, and can easily achieve non-frost operation.

Vacuum device used in the CO ₂ water heater used in the present invention method, the pre-Symbol capillary tube, as well as constituted by a capillary tube parallel structures arranged in parallel a plurality of capillary tubes, the plurality of capillary tubes each of An on-off valve is provided on the upstream side, and the on-off valve is controlled according to the load of the air heat recovery heat exchanger. At least one on-off valve has a CO ₂ refrigerant circulation line when the operation is stopped. It is possible to sufficiently cope with the cooling load fluctuation of the evaporator and the additional fluctuation caused by carrying out the operation method of the present invention which are opened so as not to block the flow of the refrigerant.

Preferably, a branch pipe is provided in the outlet side refrigerant circulation line of the gas cooler , a buffer tank is provided by interposing a relief valve in the branch pipe, and a return pipe for returning the refrigerant from the buffer tank to the circulation line is provided with an opening / closing valve. By interposing, it can fully cope with the additional fluctuation similar to the above.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of a supercritical CO ₂ refrigeration cycle to which the present invention is applied as a first embodiment, and FIG. 2 is a Mollier diagram of the supercritical CO ₂ refrigeration cycle of the present embodiment.
When the gas cooler 2 is used as, for example, a hot water supply heat source, the load of the compressor 1 varies according to the hot water supply temperature and the amount of hot water supply, and the inlet temperature of the decompression / expansion stroke also varies accordingly.

  Therefore, in this embodiment, as shown in FIG. 1, the capillary tube portion 3 that functions as the decompression / expansion stroke is composed of a plurality of capillary tubes 31 arranged in parallel, and an electromagnetic valve 32 is provided upstream of each capillary tube 31. The control device 33 is configured to perform opening / closing control of the electromagnetic valve 32 according to the load of the gas cooler 1.

4 is an air-collecting heat exchanger (evaporator) that cools the outside air with the latent heat of vaporization of the CO ₂ refrigerant, and the outside air usually fluctuates between 0 and 35 ° C. Reference numeral 5 denotes a water supply line that is supplied to cool the CO ₂ refrigerant by heat exchange in the gas cooler 2. For example, while the temperature of the CO ₂ refrigerant fluctuates from 15 ° C. to 130 ° C., heat exchange with the CO ₂ refrigerant is performed. The temperature after heat exchange varies over a range of 10 ° C to 90 ° C. Reference numeral 9 denotes a flow rate adjusting valve interposed in the water supply line 5, which automatically adjusts the flow rate of the supplied water according to the measured value of the outside air thermometer 10.

A buffer tank 6 is connected to the CO ₂ refrigerant circulation line of the refrigeration cycle by the branch pipe 7 and receives excess CO ₂ refrigerant when the load of the air heat collection heat exchanger (evaporator) 4 is small. It is acceptable. 7a is a relief valve, which is set to be opened when the pressure of the CO ₂ refrigerant circulation line exceeds 11 MPa, for example. 8 is a return pipe, and an on-off valve 8a is interposed.

If comprised in this way, even if the inlet side temperature D of the air heat collection type heat exchanger 4 fluctuates, CO ₂ passes by the opening / closing control of the electromagnetic valve 32 provided on the upstream side of each of the plurality of capillary tubes 31. As a result, the evaporation temperature on the downstream side of the capillary tube section 3 can be lowered, in other words, in the two-phase region. Can absorb fluctuations in the expansion process. In other words, while monitoring the outlet temperature of the gas cooler 2 and the temperature and pressure of the air heat collection heat exchanger 4, the opening and closing of the solenoid valve 32 is controlled to switch the capillary tube through which the refrigerant passes, so that the capillary tube portion 3 inlet side is switched. The load fluctuation of the gas cooler 2 can cope with any load fluctuation on the evaporator 4 side.

That is, in the refrigeration cycle of this embodiment, when the load fluctuates into three types of C ₁ , C ₂ , and C ₃ on the Mollier diagram shown in FIG. 1 is selected, and one of the capillary tubes 31 having the parallel structure shown in FIG. 1 that can cope with these loads is selected. For example (in the case of C ₁₎ hot water supply load of the gas cooler 2 is larger, since the transition to closer to the liquid phase, the density of the CO ₂ refrigerant increases, thus if this constant flow rate, the length of the capillary tube become longer. The smaller the hot water supply load of the gas cooler 12, the lower the density of the CO ₂ refrigerant, and thus the shorter capillary tube is required. The smaller the hot water supply load of the gas cooler 2, the lower the density of the CO ₂ refrigerant, and thus the longer the required capillary tube length. In the gas phase region, it is necessary to increase the inner diameter and length of the capillary tube.

Thus, according to the fluctuation | variation of load, the part of solenoid valve 32 corresponding to the capillary tube which can fully respond to the load in that case is opened. At the same time, the electromagnetic valve 32 is switched while observing the outlet temperature of the gas cooler 2 and the temperature and pressure of the air heat collection heat exchanger 4 as described above. By operating in this way, it is possible to cope with load fluctuations.
Therefore, as an alternative means, a temperature sensor is provided on the outlet side of the gas cooler 2, or a temperature sensor or a pressure sensor is provided on the inlet side of the air heat collecting heat exchanger 4, and the solenoid valve 32 is controlled based on the detection values of these sensors. The opening and closing may be automatically controlled.

At least one solenoid valve 32 is opened so as not to block the flow of the CO ₂ refrigerant circulation line when the operation is stopped.
Moreover, the CO ₂ refrigerant circulation mass of this refrigeration cycle is set at the maximum volume. So when the process proceeds to the operation of the C _3, the density of the CO ₂ refrigerant is decreased, CO ₂ refrigerant quantity comes excess.

When the operation is continued as it is, the pressure in the compressor 1 increases, so that excess CO ₂ refrigerant is transferred from the branch pipe 7 to the buffer tank 6. For example, in actual operation, CO ₂ mass is required 4~5Kg 10Kg, 7Kg at _{D 2,} with _{D 3} in the cycles _{D 1.} Therefore, when the cycle shifts to the cycle of C ₂ or C ₃ , since CO ₂ remains, CO ₂ is transferred to the buffer tank 6. Therefore, the relief valve 7a is set to be opened when the pressure of the CO ₂ refrigerant circulation line exceeds 11 MPa, for example.
When the operation of the refrigeration cycle is stopped, the open / close valve 8a of the return pipe 8 is opened to return the CO ₂ accumulated in the buffer tank 6 to the circulation line of the refrigeration cycle.

According to the apparatus of the first embodiment, the capillary tube portion 3 has a configuration in which a plurality of capillary tubes 31 are arranged side by side, and electromagnetic valves 32 are interposed in the respective capillary tubes 31 in accordance with the hot water supply load of the gas cooler 2. The electromagnetic valve 32 is controlled to open and close, and a buffer tank 6 that accepts unnecessary CO ₂ is provided to transfer unnecessary CO ₂ to the buffer tank 6 when the load is small. Can be handled.

As an alternative means, a temperature sensor that detects the CO ₂ refrigerant temperature is provided on the outlet side of the gas cooler 2, and an electromagnetic valve that is actuated by a signal from the temperature sensor is provided in the branch pipe 7, based on the detection value of the temperature sensor. The electromagnetic valve may be opened.
As described above, according to the first embodiment, it is possible to operate under any conditions of the refrigeration cycle having a large load fluctuation with an inexpensive structure that does not require an expansion valve. Moreover, since a complicated control system such as a step motor or a conductive expansion valve is not required, there is no malfunction and it is economical and highly reliable.

A case will be described in which the non-throttle operation of the present invention in the cold season is performed using the apparatus of the first embodiment that can cope with such fluctuations in operating conditions and loads.
The amount of water supplied to the gas cooler 2 is reduced in the cold season to prevent the air-side heat transfer surface of the air heat collection heat exchanger (evaporator) 4 from freezing. In this apparatus, the flow rate adjusting valve 9 automatically adjusts the flow rate of the water supply line 5 based on the measured value of the outside air thermometer 10.

That is, as the amount of water supplied to the gas cooler 2 decreases as the flow rate adjustment valve 9 is throttled, the CO ₂ refrigerant temperature on the outlet side of the gas cooler 2 rises, and the refrigeration cycle is gasified from the liquid phase side on the Mollier diagram of FIG. Move to the phase side.
That performed _{(A → B 2 → C 2} → D 2 → A) operation in FIG. 2, or _{(A → B 3 → C 3} → D 3 → A) operation. In this case the hot water supply load is reduced in the gas cooler 2, the CO ₂ is transferred to the gas phase side, since CO ₂ pressure is large in the compressor 1 of the present refrigeration cycle, the CO ₂ pressure exceeds a predetermined value, the relief The valve 7 a is activated, and the excess CO ₂ refrigerant is transferred to the buffer tank 6 via the branch pipe 7.

In this way, when the detected value of the outside air thermometer 10 becomes low in the cold season, the opening degree of the flow rate adjusting valve 9 is automatically throttled, thereby increasing the CO ₂ refrigerant temperature on the outlet side of the gas cooler 2. Non-frost operation can be easily performed.
According to the method of the present embodiment, it is possible to operate sensitively to the weather condition of the outside air by detecting the temperature of the outside air and reducing the amount of water supplied to the gas cooler 2 based on the measured temperature value. Therefore, reliable non-frost operation is possible. Furthermore, it is not accompanied by an extra device, is inexpensive, and can easily achieve non-frost operation.
In addition to detecting the temperature of the outside air, one or more weather conditions such as humidity, rain, and snow may be measured and the operation may be controlled based on those values.

As described above, according to the present invention, in the non-frost operation method of a CO ₂ hot water supply apparatus using an air heat collecting heat exchanger (evaporator) and having a water heater whose gas cooler cools the CO ₂ refrigerant, the temperature state by detecting the, by reducing the water amount to be supplied to the water heater on the basis of the same temperature condition, without attached an extra device, simply and with inexpensive and responsive to ambient conditions Non-frost operation in the cold season can be easily performed.

Supercritical CO ₂ refrigeration cycle according to the first embodiment of the present invention a method is a schematic configuration diagram showing. It is a Mollier diagram of a supercritical CO ₂ refrigeration cycle to which the first embodiment is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Gas cooler 3 Capillary tube part 4 Air collection type heat exchanger (evaporator)
5 Water supply line 6 Buffer tank 7 Branch pipe 7a Relief valve 8 Return pipe 8a On-off valve 9 Flow control valve 10 Outside air thermometer 32 Electromagnetic valve 33 Control device

Claims (4)

CO ₂ compressor for compressing CO ₂ refrigerant on the refrigerant circulation line, is compressed in the compressor gas cooler for cooling the gaseous refrigerant to a high temperature and high pressure, reducing the pressure of the CO ₂ refrigerant cooled in the same gas cooler A heat pump cycle is configured by sequentially interposing a capillary tube section and an evaporator for evaporating CO ₂ refrigerant that has been depressurized and cooled to a low temperature in the capillary tube section , and the gas cooler is configured to supply water from the water supply line and the CO 2 ₂ a refrigerant by heat exchange a water heater for heating the該供water supply, also the evaporator CO ₂ water heater is an air adoption thermal heat exchanger for evaporating the CO ₂ refrigerant and outdoor air heat exchanger In the device
The flow rate of the supply water supplied to the gas cooler can be adjusted based on the measured value of the outside air temperature, and a buffer tank is provided by branching a refrigerant circulation line between the outlet side of the gas cooler and the inlet side of the capillary tube, A CO ₂ hot water supply apparatus that receives and returns a CO ₂ refrigerant in response to a load of an air heat recovery heat exchanger in a buffer tank . Said capillary tube, constituted by a capillary tube parallel structures arranged in parallel a plurality of capillary tubes, the on-off valve provided on the upstream side of each of the plurality of capillary tubes, depending on the load of the air adoption thermal heat exchanger The open / close control of the open / close valve is performed , and at least one open / close valve is opened so as not to interrupt a flow of the CO ₂ refrigerant circulation line when the operation is stopped . CO ₂ water heater . CO ₂ compressor for compressing CO ₂ refrigerant on the refrigerant circulation line, is compressed in the compressor gas cooler for cooling the gaseous refrigerant to a high temperature and high pressure, reducing the pressure of the CO ₂ refrigerant cooled in the same gas cooler A capillary tube unit and a CO ₂ refrigerant that has been decompressed and cooled to a low temperature in the capillary tube unit and an evaporator that exchanges heat with the outside air to evaporate the CO ₂ refrigerant are sequentially disposed, and water is supplied by the gas cooler. Provided with a water heater that heats the feed water by exchanging heat between the feed water from the line and the CO ₂ refrigerant, thereby preventing a decrease in the evaporator outlet temperature and enabling a non-frost operation. In the non-frost operation method of the CO ₂ water heater ,
When the measured value of the outside air temperature becomes low in the cold season, the flow rate of the supply water supplied to the gas cooler is reduced to raise the gas cooler outlet temperature, and the refrigerant circulation between the outlet side of the gas cooler and the inlet side of the capillary tube section A non-frost operating method for a CO ₂ hot water supply apparatus characterized in that a buffer tank is provided by branching a line, and CO ₂ refrigerant is received and returned in response to the load of the air heat recovery heat exchanger. . Said capillary tube, constituted by a capillary tube parallel structures arranged in parallel a plurality of capillary tubes, the on-off valve provided on the upstream side of each of the plurality of capillary tubes, depending on the load of the air adoption thermal heat exchanger The open / close control of the open / close valve is performed , and at least one open / close valve is opened so as not to interrupt a flow of the CO ₂ refrigerant circulation line when the operation is stopped . Non-frost operation method for CO ₂ water heater .

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