JPH0635869U - Gas engine heat pump - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a structure for a gas engine heat pump in which engine cooling water is preheated by the heat of exhaust gas and does not discharge drain water from an exhaust gas heat exchanger to the outside of the machine. [Composition] In a gas engine heat pump equipped with an exhaust heat recovery device for preheating refrigerant entering the compressor with engine cooling water and an exhaust gas heat exchanger for preheating engine cooling water with engine exhaust gas, in an exhaust gas duct or cooling water pipe. A means for switching the exhaust gas or the cooling water to the bypass side is provided at the initial stage of engine startup, while connecting the duct or the pipe bypassing the exhaust gas heat exchanger via the switching valve. [Effect] Since the exhaust gas and cooling water do not exchange heat during the period during which condensed water is likely to be generated from the initial stage of operation to steady operation, the temperature of the exhaust gas is raised too high to eliminate drainage water. Therefore, it was possible to prevent erosion of concrete, rain gutter, etc. by acidic water while avoiding various problems that occur when the exhaust gas temperature is set to a high temperature.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a gas engine heat pump that preheats engine cooling water with engine exhaust gas.

[0002]

[Prior art]

 FIG. 1 is a schematic system diagram showing the state of the heating operation of this type of gas engine heat pump that has been conventionally performed. The engine cooling water circulating in the cooling water circuit shown by the thick line is taken away in the engine 3. The heat is radiated by the double-pipe type exhaust heat recovery unit 2 to preheat the refrigerant and then supplied to the engine 3 by the circulation pump 12, but the heat of the exhaust gas of the engine 3 is also effectively used. Therefore, an exhaust gas heat exchanger 4 for preheating engine cooling water with exhaust gas is provided.

[0003]

[Problems to be solved by the device]

 However, in the above-mentioned conventional configuration, the water contained in the exhaust gas is condensed and discharged as drain water. However, since this drain water is acidified by the NOx and other components being dissolved, it remains as it is. When discharged, there was a problem of eroding the concrete surface of the outdoor unit installation location and the rain gutter. Therefore, in order to prevent the drain water from being discharged, it is possible to raise the temperature of the exhaust gas to such an extent that moisture does not condense from the exhaust gas, but this will decrease the heating efficiency and raise the temperature of the exhaust system. For this reason, rubber pipes cannot be used. If metal pipes are used as a countermeasure, there is a problem that fatigue damage easily occurs due to engine vibration. It is an object of the present invention to solve such problems and to provide a structure of a gas engine heat pump that does not discharge drain water without raising the exhaust gas temperature too much.

[0004]

[Means for Solving the Problems]

 The gas engine heat pump according to the present invention includes an exhaust heat recovery unit 2 for preheating the refrigerant supplied to the compressor 1 with engine cooling water, as shown in the embodiment of FIGS. In a gas engine heat pump provided with an exhaust gas heat exchanger 4 for preheating engine cooling water with exhaust gas of the engine 3, the exhaust gas heat exchanger 4 is connected to an exhaust gas duct 5 or a cooling water pipe 6 via a switching valve 7. The bypass duct 5a for bypassing or the bypass pipe 6a is connected, and a control device 8 for switching exhaust gas or cooling water to the bypass side is provided at the initial stage of engine startup.

[0005]

[Action]

 According to the above configuration, the exhaust gas does not pass through the exhaust gas heat exchanger 4 at a low temperature in which condensed water is relatively likely to be generated in the initial stage of engine startup, the exhaust gas temperature becomes sufficiently high, and the water in the exhaust gas is collected in the cooling water coil. After the exhaust gas does not condense, the exhaust gas can be passed through the exhaust gas heat exchanger to preheat the cooling water. Therefore, it suffices to design the heat transfer area of the exhaust gas heat exchanger 4 just to a size such that drain water does not come out during steady operation, and it is not necessary to raise the discharge temperature of the exhaust gas so much, so the exhaust heat utilization efficiency Can be reduced to a minimum.

[0006]

【Example】

 FIG. 1 is a schematic system diagram of an outdoor unit of a gas engine heat pump according to the present invention, and a solid line shows a state during heating operation. In the figure, a compressor 1 which constitutes a heat pump is driven by a water-cooled gas engine 3, and the refrigerant is compressed to a high temperature by the compressor 1 and then radiated by an indoor unit B through a solid line passage of a four-way valve 9. Then, it is expanded and vaporized by the expansion valve 10 and liquefied while depriving the heat of vaporization by the outdoor heat exchanger 11 and the exhaust heat recovery device 2, and enters the compressor 1. On the other hand, the engine cooling water is circulated by the circulation pump 12 along the thick line to cool the engine 3, and then the exhaust heat recovery unit 2 transfers the exhaust heat of the engine 3 to the cooling medium. An exhaust gas heat exchanger 4 is provided in order to effectively use the exhaust gas, and the engine cooling water is preheated by the exhaust gas heat exchanger 4. Reference numeral 15 is a radiator, which is inserted into the cooling water circuit by a temperature control valve 16 during cooling operation. The structure up to this point is the same as the conventional one, and the present invention is characterized by the structure of the exhaust gas heat exchanger 4, as described below.

In the embodiment shown in FIG. 2, the exhaust gas duct 5 is connected to a bypass duct 5a that bypasses the exhaust gas heat exchanger 4 via a switching valve 7, and the control device switches to the exhaust gas bypass side at the initial stage of engine startup. 8 is provided. Reference numeral 17 denotes a water temperature sensor provided near the engine outlet of the cooling water pipe 6. When the temperature detected by the water temperature sensor 17 exceeds a specified value, the control device 8 switches the switching valve 7 to the exhaust gas heat exchanger 4 side. It is like this. According to this configuration, heat exchange between the exhaust gas and the cooling water is not performed while the temperature of the exhaust gas is relatively low at the initial stage of engine startup and water is likely to condense from the exhaust gas, but heat is exchanged after the exhaust gas temperature rises sufficiently. Since it can be done, condensed water is not generated and it is not necessary to discharge drain water outside the machine. In addition, the exhaust gas discharge temperature can be set so that condensed water does not generate during steady operation, and drain water can be eliminated without raising the exhaust gas temperature too much, so heating efficiency does not decrease significantly. I'm done.

In the embodiment shown in FIG. 3, the cooling water pipe 6 is connected with a bypass pipe 6b that bypasses the exhaust gas heat exchanger 4 via switching proportional valves 7a and 7b, and a water temperature sensor 17 and a control valve are connected. The control device 8 switches the cooling water to the bypass side at the initial stage of engine startup. In the configuration shown in the figure, the proportional valve 7a on the exhaust gas heat exchanger 4 side is closed and the proportional valve 7b on the bypass side is opened for several seconds after the engine is started. Next, the valve 7a is slightly opened, and thereafter, the opening degrees of both valves 7a and 7b are controlled so that the temperature detected by the water temperature sensor 17 is maintained at a specified value or higher. Of course, instead of switching proportionally as described above, one switching valve 7 may be used as shown in FIG. 2 to switch at once when the detected temperature reaches a constant value.

FIG. 4 shows another embodiment, in which the radiator 15 of the cooling water circuit and the outdoor heat exchange of the refrigerant circuit are replaced with the exhaust heat recovery device 2 comprising the double-tube heat exchanger of FIG. The exhaust heat recovery unit 2 is constructed by winding each coil of the device 11 around a common fin to reduce the cost. A gas engine heat pump having such a structure is also shown in Figs. It goes without saying that the present invention can be implemented as described above.

[0010]

[Effect of device]

 As described above, in the present invention, exhaust gas or engine cooling water bypasses the exhaust gas heat exchanger during the period when condensed water is easily generated from the initial stage of operation to steady operation, so the exhaust gas temperature is sufficiently high. It is sufficient to design the heat transfer area of the exhaust gas heat exchanger so that condensed water is not generated only during steady operation, and it is not necessary to make the heat transfer area too small. While avoiding problems, it has the advantage that it can prevent erosion of concrete and gutters by acid water.

[Brief description of drawings]

FIG. 1 is an overall system diagram showing an example of a gas engine heat pump targeted by the present invention.

FIG. 2 is a system diagram of a main part of the above.

FIG. 3 is a main part system diagram of another embodiment of the present invention.

FIG. 4 is an overall system diagram showing still another embodiment of the present invention.

[Explanation of symbols]

 1 Compressor 2 Exhaust Heat Recovery Device 3 Gas Engine 4 Exhaust Gas Heat Exchanger 5 Exhaust Gas Duct 5a Bypass Duct 6 Cooling Water Piping 6a Bypass Piping 7 Switching Valves 7a, 7b Switching Proportional Valve 8 Controller A Outdoor Unit B Indoor Unit

Claims (1)

[Scope of utility model registration request] 1. A gas engine heat pump comprising an exhaust heat recovery device for preheating refrigerant supplied to a compressor with engine cooling water and an exhaust gas heat exchanger for preheating engine cooling water with engine exhaust gas, in an exhaust gas duct or A gas engine heat pump comprising a cooling water pipe connected to a duct or a pipe bypassing the exhaust gas heat exchanger via a switching valve, and provided with means for switching exhaust gas or cooling water to the bypass side at the initial stage of engine startup.