Method and device for controlling operation of heat pump unit

Abstract

The temperature of high-temperature water at the exit of a condenser is maintained to be within a setting range by control of, under an operation with all cylinders, capacity of a reciprocating compressor in the period between a maximum allowable load and a minimum load for lubrication, at which the flow of a lubrication oil pump is ensured, based on the revolution-speed control of a drive motor that drives the reciprocating compressor and by control of the capacity of the reciprocating compressor at the minimum load for lubrication or less based on the combination of the control of decreasing the number of operation cylinders and the revolution-speed control of the drive motor. In addition, a heating mechanism is provided on an inlet path of the reciprocating compressor to prevent the liquefied refrigeration flow of a refrigerant liquid to the reciprocating compressor during the operation or at the start.

Description

TECHNICAL FIELD[0001]The present invention relates to an operation control method and an operation control unit that implement the stable supply of high-temperature water or low-temperature water at desired temperature by means of a heat pump unit that uses an NH3 refrigerant.BACKGROUND ART[0002]From the viewpoint of global environmental protection, natural refrigerants having a small ozone depletion potential (ODP) and a small global warming potential (GWP) have been conventionally promoted as operation refrigerants for heat pump units instead of chlorofluorocarbons. Since CO2 serving as a natural refrigerant has a small ODP of 0 and a small GWP of 1, allows high-temperature hot-water supply, and has high COP, it has been practically used in hot-water supply machines for home and business uses.[0003]However, the CO2 refrigerant has higher pressure than general refrigerants at ambient atmospheric temperature and thus cannot be used in existing equipment. Therefore, equipment support...

AI Technical Summary

Benefits of technology

The present invention provides a unit for controlling an operation of a heat pump unit that uses NH3 as a refrigerant, which includes a compressor, condenser, expansion valve, and evaporator. The unit includes a temperature sensor and a controller that keep the temperature of the heat-exchanging fluid at the exit of the condenser or the evaporator within a range. The controller maintains the temperature by controlling the capacity of the reciprocating compressor and the flow of the lubrication oil pump based on the revolution-speed control of the drive motor and the cylinder-number control. This invention prevents damage to equipment and components by eliminating liquefied refrigeration flow to the compressor during operation or at the stop of the operation. The technical effect of this invention is to ensure the safe and efficient operation of the heat pump unit.

Problems solved by technology

However, the CO2 refrigerant has higher pressure than general refrigerants at ambient atmospheric temperature and thus cannot be used in existing equipment.

Therefore, equipment supporting the pressure of CO2 is required to be newly constructed besides a pipe system, which gives rise to the problem that an equipment expense becomes high.

Therefore, the pressure of the refrigerant depends on fluctuation factors such as operation conditions and ambient temperature, which gives rise to the problem that the refrigerant-side surface temperature of an inlet pipe, the compressor, and an outlet pipe at the stop and that of the inlet pipe and the compressor during the operation fall below the saturation temperature of the pressure of the NH3 refrigerant gas to liquefy the NH3 refrigerant gas.

Furthermore, if the pressure of the NH3 refrigerant gas of the inlet path of the compressor is increased, the temperature of the inlet pipe cannot follow such an increase, which results in the likelihood of the high-temperature NH3 refrigerant gas being brought into contact with the inlet pipe and liquefied.

In case that the compressor sucks the liquefied refrigerant in, the metal contact of a piston, a piston ring, or the like occurs, which may cause damage on equipment and components.

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