JP2005147437A - Heat pump device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the reliability of a compressor by preventing a temperature rise of the compressor caused by overshoot of a discharge temperature. <P>SOLUTION: In this heat pump device comprising a refrigerant circuit and a discharge temperature sensor 15 for detecting a discharged-refrigerant temperature of the compressor 11, a discharge temperature control means 23 is mounted for stabilizing the discharge temperature in starting the operation of the compressor 11 on the basis of a target discharge temperature, after the discharge temperature is almost stabilized on the basis of the initial discharge temperature slightly lower than the target discharge temperature. Thereby the overshoot of the discharge temperature of the compressor 11 in starting the operation can be prevented, and the reliability of the compressor 11 can be improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat pump apparatus including a compressor.

In a conventional heat pump device, a method of controlling the opening degree of the expansion valve so that the superheat (superheat degree) of the refrigerant sucked in the compressor is within 0 to 5K is generally used as the expansion valve control during operation (for example, non-patent) Reference 1). This expansion valve control method is applicable not only to the heat pump cycle but also to the vapor compression refrigeration cycle in general, and has a relatively simple configuration (not shown) of a compressor suction refrigerant temperature sensor and a compressor suction pressure sensor. Efficient refrigeration cycle control can be performed.
Fumio Matsuoka "Dynamic characteristics and control of refrigeration cycle", Refrigeration, July 2003, Vol. 78, No. 909, P60-P65

  However, in the above-described conventional configuration, when the operation is started, the discharge refrigerant temperature of the compressor (hereinafter referred to as discharge temperature) causes an overshoot relative to the stable discharge temperature. In other words, the discharge temperature rises with the start of operation, and once the temperature becomes higher than the stable discharge temperature, the discharge temperature decreases and then stabilizes at the stable discharge temperature.

  When this discharge temperature overshoot becomes large, there is a risk of adversely affecting the reliability of the compressor in a refrigeration cycle that employs a high-pressure shell type compressor and has a high discharge temperature during operation. For example, in a supercritical cycle heat pump water heater that can produce hot (90 ° C.) hot water with high efficiency, the discharge temperature when the heat pump cycle is stable is 100 ° C. to 120 ° C., and the motor coil temperature in the compressor at that time is Furthermore, the temperature is high. If the discharge temperature overshoot at the start of operation described above is added, the inside of the compressor will be exposed to a higher temperature environment, deterioration of the insulation performance of the motor coil due to high temperature, seizure of the compressor sliding part, etc. There is a possibility that the reliability of the compressor may be impaired, and in the worst case, the compressor may be damaged.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a heat pump device that can prevent an overshoot of a discharge temperature at the time of starting operation.

  In order to solve the conventional problems, a heat pump device according to the present invention includes a refrigerant circuit in which a compressor, a gas cooler, an expansion valve, and a heat exchanger are connected in an annular shape, and a discharge temperature sensor that detects a discharge refrigerant temperature of the compressor. And a discharge temperature control means for stabilizing the discharge temperature at the start of operation of the compressor to the target discharge temperature after substantially stabilizing the discharge temperature to an initial discharge temperature lower than the target discharge temperature.

  Thereby, the overshoot of the discharge temperature at the time of starting operation can be prevented.

  The heat pump device of the present invention can prevent overshoot of the discharge temperature at the start of operation, and can improve the reliability of the compressor.

  A first invention includes a refrigerant circuit in which a compressor, a gas cooler, an expansion valve, and a heat exchanger are connected in an annular shape, a discharge temperature sensor that detects a discharge refrigerant temperature of the compressor, and a discharge when the compressor is started up. By providing the discharge temperature control means for stabilizing the temperature to the target discharge temperature after substantially stabilizing the temperature to the initial discharge temperature lower than the target discharge temperature, it is possible to prevent overshoot of the discharge temperature at the start of operation, It is possible to improve the reliability of the compressor.

  In the second invention, in particular, by setting the temperature difference between the initial discharge temperature and the target discharge temperature of the heat pump device of the first invention to a value between 3K and 5K, the discharge temperature overshoot at the start of operation In addition, the heat pump cycle can be quickly started up.

  In the heat pump device of the first or second invention, the third aspect of the invention is that the discharge temperature at the start-up of the operation is set by setting the time for substantially stabilizing the initial discharge temperature to a value between 5 minutes and 10 minutes. The heat pump cycle can be quickly activated while preventing overshoot.

  In the fourth aspect of the invention, in particular, the refrigerant circuit in the heat pump device according to any one of the first to third aspects of the invention is supercritical heat pump cycle in which the pressure of the refrigerant is equal to or higher than the critical pressure, so that the pressure is increased to the critical pressure or higher. By heating the water or air of the gas cooler with the refrigerant, the refrigerant in the gas cooler is pressurized above the critical pressure, so it can condense even if the temperature drops due to heat being taken away by the water or air of the gas cooler. Absent. Therefore, it becomes easy to form a temperature difference between the refrigerant and water or air in the entire area of the gas cooler, and hot water (about 90 ° C.) or air can be obtained, and the heat exchange efficiency can be increased.

  In the fifth aspect of the invention, in particular, the refrigerant of the heat pump device of the fourth aspect is carbon dioxide. Since the carbon dioxide refrigerant is relatively inexpensive and stable, the product cost can be reduced and the reliability can be improved. it can. In addition, carbon dioxide has an ozone depletion coefficient of zero and a global warming coefficient of about 1/700 of the alternative refrigerant HFC-407C, which is very small.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a configuration diagram of the heat pump device according to the first embodiment of the present invention applied to a heat pump water heater.

  In FIG. 1, the heat pump unit 16 includes a refrigerant circuit in which a compressor 11, a refrigerant side pipe 12 of a gas cooler, an electric expansion valve 13, and an outdoor heat exchanger 14 are connected in an annular shape, and a discharge side pipe of the compressor 11. In the middle, a discharge temperature sensor for detecting the compressor discharge refrigerant temperature is installed. The discharge temperature control means 23 controls the opening degree of the electric expansion valve 13 so that the discharge refrigerant temperature of the compressor 11 during operation of the heat pump unit 16 becomes a predetermined temperature.

  The tank unit 22 includes a hot water tank 17, a circulation pump 18, a hot water supply circuit that connects the water-side pipes 19 of the gas cooler in an annular shape, an incoming water temperature sensor 20 that detects an inlet temperature of the water-side pipe 19 of the gas cooler, and a gas cooler A hot water temperature sensor 21 that detects the outlet temperature of the water side pipe 19 is configured. The water in the hot water storage tank 17 is conveyed by the circulation pump 18 to the water side pipe 19 of the gas cooler, where it is heated to high temperature hot water by exchanging heat with the high temperature refrigerant in the refrigerant side pipe 12 of the gas cooler. Note that the temperature of the hot water is controlled by increasing or decreasing the flow rate of the circulation pump 18.

  About the heat pump apparatus comprised as mentioned above, the operation | movement and an effect | action are demonstrated below. FIG. 2 is a flowchart illustrating control of the heat pump apparatus according to the first embodiment of this invention. In the heat pump device according to the first embodiment of the present invention, a case where the target hot water temperature is set to 90 ° C. and the target discharge temperature is set to 110 ° C. will be described.

  In FIG. 2, when a boiling operation instruction is given, in STEP 1, the operation frequency of the compressor 11, the opening degree of the electric expansion valve 13, the flow rate of the circulation pump 18, etc. are set and the operation is started. Next, in STEP 2, the opening degree of the electric expansion valve 13 is controlled by the discharge temperature control means 23 so that the detected value of the discharge temperature sensor 15 becomes the initial discharge temperature. Here, the initial discharge temperature is set lower than the target discharge temperature, and the temperature difference is preferably a value between 3K and 5K. First, in view of the accuracy of the discharge temperature sensor 15, if the temperature difference is less than 3K, there is no significant difference between the initial discharge temperature and the target discharge temperature. Also, if the temperature difference is greater than 5K, the range of change when the control target shifts from the initial discharge temperature to the target discharge temperature becomes large, which may cause overshoot with respect to the target discharge temperature. is there. In this embodiment, the initial target discharge temperature is set to 105 ° C. (a value 5K lower than the target discharge temperature 110 ° C.). After the start of operation, the discharge temperature rises, eventually falls slightly after the initial discharge temperature, and stabilizes at 105 ° C. At this time, the target discharge temperature of 110 ° C. is not exceeded.

  In STEP 3, the case where the detected value of the discharge temperature sensor 15 is within 105 ° C. ± 1 K is determined to be substantially stable, and when the substantially stable holding time becomes 10 minutes or more, the process proceeds to STEP 4 and the discharge temperature sensor 15 The opening of the electric expansion valve 13 is controlled so that the detected value becomes the target discharge temperature (110 ° C.). At this time, since the change width from the initial discharge temperature (105 ° C.) to the target discharge temperature (110 ° C.) is relatively small as 5K, the discharge temperature overshoot, that is, the detected value of the discharge temperature sensor 15 is 110 of the target discharge temperature. It can be prevented from exceeding ℃.

  Therefore, the abnormal temperature rise of the compressor 11 can be prevented and the reliability can be improved.

  As described above, in the present embodiment, the discharge temperature control means for stabilizing the discharge temperature at the start of operation of the compressor 11 to the target discharge temperature after being substantially stabilized at the initial discharge temperature slightly lower than the target discharge temperature. 23 is provided, it is possible to prevent an overshoot of the discharge temperature at the start of operation, and to improve the reliability of the compressor 11.

  As described above, the heat pump device according to the present invention is particularly effective when applied to a vapor compression refrigeration cycle equipped with a high-pressure shell type compressor. Moreover, the heat pump apparatus of this invention can be utilized for an air-conditioner, a refrigerator, etc. other than a water heater.

Configuration diagram of heat pump device in Embodiment 1 of the present invention The flowchart explaining control of the heat pump apparatus in Embodiment 1 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Compressor 12 Gas cooler refrigerant side piping 13 Electric expansion valve 14 Outdoor heat exchanger 15 Discharge temperature sensor 16 Heat pump unit 17 Hot water storage tank 18 Circulation pump 19 Gas cooler water side piping 20 Incoming water temperature sensor 21 Hot water temperature sensor 22 Tank unit 23 Discharge Temperature control means

Claims (5)

A refrigerant circuit in which a compressor, a gas cooler, an expansion valve, and a heat exchanger are connected in an annular shape, a discharge temperature sensor that detects a discharge refrigerant temperature of the compressor, and a discharge temperature at the start of operation of the compressor from a target discharge temperature A heat pump apparatus comprising discharge temperature control means for stabilizing the target discharge temperature after being substantially stabilized at a low initial discharge temperature. The heat pump device according to claim 1, wherein the temperature difference between the initial discharge temperature and the target discharge temperature is set to a value between 3K and 5K. The heat pump device according to claim 1 or 2, wherein the time for substantially stabilizing the initial discharge temperature is set to a value between 5 minutes and 10 minutes. The refrigerant circuit is a supercritical heat pump cycle in which a refrigerant pressure on a high-pressure side is equal to or higher than a critical pressure, and heats water or air of a gas cooler with the refrigerant whose pressure is increased to the critical pressure or higher. The heat pump device described in 1. The heat pump device according to claim 4, wherein the refrigerant is carbon dioxide.

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