Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2001-06-04
2002-10-22
Doerrler, William C (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S210000
Reexamination Certificate
active
06467289
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to Japanese Patent Applications No. 2000-167510 filed on Jun. 5, 2000, No. 2000-344206 filed on Nov. 10, 2000, and No. 2001-116959 filed on Apr. 16, 2001, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat-pump type hot-water supply system, and more particularly, relates to technique for restraining a decrease of boiling-up ability resulting from an increase in a water temperature in a final stage of boiling-up and for reducing running cost by optimizing a boiling-up terminating condition.
2. Description of Related Art
Applicants of the present application invented a hot-water supply system with a heat pump cycle which includes a refrigerant compressor, a refrigerant flow passage of a water heat exchanger, an expansion valve, an air heat exchanger provided with an outdoor fan, and a hot water circuit. In the hot water circuit, a hot-water storage tank for storing hot water for a hot-water supply and a hot-water flow passage of the water heat exchanger are connected through a hot-water pipe, and a pump is provided in the hot-water pipe between the hot-water storage tank and the hot-water flow passage. In addition, a difference between a refrigerant temperature at an outlet side of the refrigerant flow passage and a hot-water temperature at an inlet side of the hot-water flow passage is compared with a target temperature difference, and a valve opening degree of the expansion valve is controlled to improve a cycle efficiency (coefficient of performance, COP).
When the temperature of the hot-water within the hot-water circuit is high, it becomes difficult to cause a temperature difference between the refrigerant temperature on the outlet side of the refrigerant flow passage and the hot-water temperature on the inlet side of the hot-water flow passage, and the expansion valve is controlled in a direction that opens the expansion valve. As a result, a high-pressure side refrigerant pressure within the heat pump cycle becomes lower. Particularly, when temperature of hot-water within the hot-water storage tank has lowered by stopped operation for many hours and thereafter the hot-water is boiled up again, or when the temperature of hot-water within the hot-water circuit including the hot-water storage tank is ununiform, there arises a problem.
In addition, because the temperature of hot water in the hot water circuit increases with an elapse time of operation of the hot-water supply system, the temperature difference between the refrigerant temperature on the outlet side of the refrigerant flow passage and the hot-water temperature on the inlet side of the hot-water flow passage becomes smaller in a final stage of boiling up of hot water, and the control of the expansion valve due to the temperature difference becomes difficult.
SUMMARY OF THE INVENTION
In view of the foregoing problems, it is an object of the present invention to provide a hot-water supply system with a heat pump cycle, capable of preventing a decrease of hot-water supply ability due to a lowered refrigerant pressure within the heat pump cycle.
It is a second object of the present invention to provide a hot-water supply system with a heat pump cycle, capable of resolving insufficient ability and securing a target hot-water supply temperature during a boiling-up operation without adding any new functional components, and improving stability and reliability of a hot-water control in low cost.
A third object according to the present invention is to provide a hot-water supply system with a heat pump cycle, in which the boiling-up operation is performed in consideration of electric power rate per unit time based on a time-of-day rate system, and running cost is reduced.
It is a fourth object of the present invention to provide a hot-water supply system with a heat pump cycle, which accurately perform a control immediately before boiling-up.
According to an aspect of the present invention, in a hot-water supply system, a control unit controls operation of an expansion valve in a first direction increasing an opening degree of the expansion valve, when a temperature difference, between a refrigerant temperature at an outlet side of a refrigerant passage in a fluid heat exchanger and a fluid temperature at an inlet side of a fluid passage in the fluid heat exchanger, is smaller than a target temperature difference. On the other hand, the control unit controls operation of the expansion valve in a second direction decreasing the opening degree of the expansion valve, when the temperature difference is larger than the target temperature difference. In addition, when the temperature difference is smaller than the target temperature difference and the expansion valve is controlled in the first direction, the control unit controls a high-pressure side refrigerant pressure before being decompressed in the heat pump cycle to be equal to or higher than a predetermined refrigerant pressure in such a manner that the fluid has the target fluid temperature. Accordingly, it is possible to maintain the high-pressure side refrigerant pressure of the heat pump cycle to exceed the predetermined refrigerant pressure, and the target supply temperature of the fluid can be secured in the hot-water supply system. As a result, the hot-water supply system can prevent a decrease of hot-water supply ability due to a lowered refrigerant pressure within the heat pump cycle.
According to an another aspect of the present invention, in a hot-water supply system, when the control unit determines a heat radiation from the refrigerant to air in an air heat exchanger, the control unit controls a high-pressure side refrigerant pressure before being decompressed in the heat pump cycle to be equal to or higher than a predetermined refrigerant pressure at least until the heat radiation stops. Therefore, the high-pressure side refrigerant pressure in the heat pump cycle can be maintained at a pressure equal to or larger than the predetermined pressure, and the target hot-water supply temperature can be obtained without a heat loss when the fluid is water.
According to a further another aspect of the present invention, in a hot-water supply system, when the fluid temperature at the inlet side of the fluid passage in the fluid heat exchanger exceeds a predetermined temperature, the control unit sets a target pressure to an upper limit pressure that is lower than a compression resistance pressure of materials constituting the heat pump cycle, so that the high-pressure side refrigerant pressure of the heat pump cycle corresponds to the target pressure. Therefore, the high-pressure side refrigerant pressure in the heat pump cycle can be maintained at a pressure equal to or larger than the predetermined pressure, and the target hot-water supply temperature can be obtained when the fluid is water.
Preferably, the control unit presumes the high-pressure side refrigerant pressure based on the fluid temperature on the inlet side of the fluid passage in the fluid heat exchanger and the refrigerant temperature on the inlet side of an air heat exchanger, and increases or decreases the valve opening degree of the expansion valve in such a manner that this presumed refrigerant pressure corresponds to the upper limit pressure. Accordingly, when a relationship between the refrigerant temperature on the inlet side of the air heat exchanger and the high-pressure side refrigerant pressure is set in graphical or map based on for each fluid temperature on the inlet side of the fluid passage in the fluid heat exchanger, the high-pressure side refrigerant pressure will be presumed, based on the fluid temperature on the inlet side of the fluid passage in the fluid heat exchanger and refrigerant temperature on the inlet side of an air heat exchanger. Since there is no need to provide a high-pressure side refrigerant pressure sensor, cost for the component can be reduced and a maintenance for the high-pressure side refrig
Kobayakawa Tomoaki
Kuroki Jyouji
Kusakari Kazutoshi
Saikawa Michiyuki
Sakakibara Hisayoshi
Denso Corporation
Doerrler William C
Harness Dickey & Pierce PLC
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