JPS58217159A - Heat-pump water heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat pump water heater, and is intended to improve the characteristics at low temperatures.

First, the basic configuration of a heat pump water heater will be explained with reference to FIG.

The basic operation of the heat pump water heater will be explained below according to the diagram. 1 is a heat pump heating unit, and a compressor 2, a heating heat exchanger 3, a throttle mechanism 4, and a heat source heat exchanger 5 are connected as shown in the figure through annular refrigerant piping to form a heat pump heating cycle. The heating heat exchanger 3 is heated by the pumped up heat. The heating heat exchanger 3 and the hot water storage tank 6 covered with a heat insulating material are connected through water pipes 7 and 7' as shown in the figure to form a water circulation circuit, and this circuit includes a capacity control circuit 8 driven by a capacity control circuit 8. A controlled circulation pump 9 is provided. That is, the water in the hot water storage tank 6 is supplied from the circulation water supply port 1o provided below the hot water storage tank 6, and the water piping is connected to the circulation pump 9, the water piping 7, the heating heat exchanger 3, and the upper part of the hot water storage tank 6. 7' It flows into the hot water storage tank 6. As a result, water at temperature Tw in the hot water storage tank 6 is drawn into the circulation circuit from the lower part of the hot water storage tank 6, heated to temperature TH by the heating heat exchanger 3, and then circulated and stored from the upper part of the hot water storage tank 6. At this time, the hot water temperature is detected by a temperature detector 11 such as a thermistor that detects the hot water temperature at the outlet of the heating heat exchanger 3, and the capacity control circuit 8 adjusts the detected hot water temperature to the set hot water temperature TH3 (TH3''TH).
The circulation amount of the circulation pump 9 is controlled.

In this way, by controlling the capacity of the circulation pump 9 and controlling the hot water temperature at the outlet of the heating heat exchanger to around a certain set value, high-temperature hot water can be stored in a short time, and furthermore, the heating heat exchanger 3 can be By creating a counterflow with the refrigerant, the heat pump water heating apparatus has many features such as being able to obtain hot water at a temperature higher than the refrigerant condensation temperature by utilizing the high temperature discharge gas temperature of the compressor 2. Note that 12 is a city water supply port, 13 is a pressure reducing check valve, 14 is a hot water supply port, 15 is a hot water tap, 16 is a safety valve, 17 is an auxiliary heating device such as a heater, and 18 is a heat source blower.

Next, the unique characteristics and problems of the heat pump water heater having the above configuration will be described below.

A typical heat pump cycle without compressor capacity control has a characteristic of heat source enthalpy (heat amount possessed by the heat source).
The heating capacity changes depending on the

In other words, as shown in Figure 2a, if the compressor rotational speed is kept at a constant value and the set hot water temperature TH3 is maintained at a constant value as shown in Figure 2, the heating capacity will decrease as the heat source enthalpy decreases as shown in Figure 2. It decreases like C.

As the heating capacity decreases, the capacity of the circulation pump 9 is controlled to maintain the hot water temperature TH at a constant value, and the amount of circulating water decreases as shown in FIG. The heat pump operating time increases as shown in Figure 2e.

That is, when the set hot water temperature is always maintained at a constant value, as the heat source enthalpy decreases, the heating capacity decreases and the operating time increases. Here, the heat source ental e that allows the operation of the system. The minimum value h0 (for example, in the case of an air heat source method, the minimum enthalpy that does not cause frost formation on the heat source heat exchanger,
Or, in the case of a water heat source method, the lowest enthalpy without freezing), the heat source enthalpy. Various problems occur before the temperature declines. In other words, the heat pump operation time increases due to the reduction in heating capacity, and it takes an unreasonably long time to obtain the desired hot water temperature and amount.Also, the capacity control range increases because the amount of circulating water needs to be extremely reduced. However, there are problems such as the pump circulation volume control being easily unstable.

In particular, when used as a hot water device that uses late-night power, it is necessary to store a predetermined amount of heat within the 8-hour late-night power supply period. Therefore, depending on the hot water storage tank capacity, set hot water temperature, and supply water temperature, there is a required minimum heating capacity as shown in Figure 2 C, and if the heating capacity is less than this, it will be difficult to secure the specified amount of heat within the specified time. .

Especially in the winter, when heating to a medium temperature of, for example, 6°C using a heat pump, and then heating to a high temperature of 85°C with an auxiliary heating device such as a backup heater after the heat pump heating is completed, the minimum heating capacity is the minimum heating capacity. If the heat pump capacity is reduced below, the operating time of the compressor will increase unnecessarily, and it will be difficult to complete heat storage within a predetermined time. Particularly in the case of backup electric heaters, the practical limit for the heater capacity is 3.4 to 4 kW, and excessively extending the operation time of the heat pump will lead to a decrease in the amount of heat storage and ensure the necessary hot water supply capacity. Things become difficult.

The present invention is based on the above-mentioned problems, and in particular, it is intended to ensure the heating capacity of a water heater at all times above a certain value, thereby guaranteeing the hot water supply capacity and preventing unnecessary extension of operating time.

In order to achieve the above object, the present invention makes the capacity of the compressor variable and controls the capacity of the compressor based on the heat source enthalpy and heater inlet water temperature signals to ensure the required heat pump heating capacity. Even if the enthalpy and initial water temperature of the hot water storage tank (heater inlet water temperature) change, the required heating capacity is always exhibited, the amount of circulating water remains constant, and the heat pump operation time remains constant, ensuring the desired hot water temperature and The disadvantage that it takes an unreasonably long time to obtain the amount of hot water is eliminated.

Furthermore, since the control range of the amount of circulating water becomes smaller, the pump circulation amount control becomes extremely stable.

An embodiment of the present invention will be described below with reference to FIG. In the figure, 19 is a heat source enthalpy detection sensor, 2o is a heater inlet water temperature detection sensor, and these sensors 19,
The control circuit 21 receives the signal 20 and controls the capacity of the compressor 2. The control circuit 21 decreases the rotation speed of the compressor 2 when the heat source enthalpy increases, increases the rotation speed of the compressor 2 when the heat source enthalpy decreases, and decreases the rotation speed of the compressor 2 when the heating inlet water temperature increases. When the water temperature becomes low, the rotation speed of the compressor 2 is controlled to be increased so as to exhibit the required heating capacity. Initial water temperature in hot water tank 6 (heating heat exchanger inlet water temperature)
As shown in FIG. 3, the required heating capacity of the heat pump to heat the water to the set water temperature in a predetermined time increases linearly as the initial water temperature decreases. In addition, when the initial water temperature is constant, if the heat pump heating capacity is constant regardless of the change in heat source enthalpy, the water can be heated to the set temperature within a predetermined time, but the compressor rotation speed and heat source enthalpy are not enough to keep the heat pump heating capacity constant. As shown in FIG. 4a, the relationship increases linearly as the heat source enthalpy decreases. Therefore, even if the heat source enthalpy and the initial water temperature of the hot water storage tank 6 change, the control coefficient of the rotation speed N of the compressor 2, which always exerts the required heating capacity, is determined by the heat source enthalpy h and the initial water temperature (heating heat exchanger inlet water temperature TVv). ) can be approximated as a binary-order function N=f(h, Tw).

The operation will be explained in more detail by controlling the rotation speed of the compressor 20 according to the heat source enthalpy and the heater inlet water temperature to ensure the required heat pump heating capacity as described above. FIGS. 4a to 4e show operating operations when the control circuit 21 of this embodiment is used. Assuming that the required heating capacity QH is determined when the water temperature at the inlet of the heating heat exchanger is constant as shown in Figure 4C, if the heat source enthalpy is high, the rotation speed will be set to low, and if the heat source dual value is low, the rotation speed will be set to high. Control the compressor rotation speed to the rotation speed. Then, since the heating capacity of the heat pump is kept constant at the predetermined heating capacity QH(e'),
As shown in Fig. 4, the amount of water circulated by the circulation pump 9 to keep the set hot water temperature TH constant is kept constant as shown in Fig. 4 d, and the operating time of the heat pump is also kept constant as shown in Fig. 4 e. can be kept.

As shown in Figure 3, in response to changes in the water temperature at the inlet of the heating heat exchanger, the required heating capacity of the heat pump for heating within a predetermined time is linearly controlled by the water temperature at the heating heat exchanger. By doing so, both the circulation flow rate of the circulation pump 9 and the heat pump operation time can be kept constant.

As explained above, according to the present invention, when the heat source enthalpy is high, the rotation speed is low, when the heat source enthalpy is low, the rotation speed is high, and when the heating heat exchanger inlet water temperature is high, the rotation speed is low.
When the heating heat exchanger inlet water temperature is low, the compressor rotation speed is controlled at a high rotation speed as a binary function of the heat source enthalpy and the heating heat exchanger inlet water temperature, and the compressor is operated so that the required heating capacity is always exerted. This has the following effects. That is,
Even when the heat source enthalpy is low, heating capacity is always ensured regardless of the initial water temperature of the hot water storage tank, so it is possible to secure a predetermined amount of heat storage within a predetermined time, and it is possible to improve usability. Since the circulation flow rate remains constant, the time required to control the circulation pump capacity becomes smaller, and stable pump control becomes possible.

It goes without saying that the present invention is applicable to either an air heat source method or a water heat source method. In addition, in the case of an air heat source method in which it is difficult to directly detect the heat source enthalpy, it is also possible to conveniently substitute the heat source air temperature. i! The detection of the water temperature at the inlet of the heating heat exchanger may be replaced by the detection of the water temperature at the lower part of the hot water storage tank 6.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a heat pump water heating system according to an embodiment of the present invention, Fig. 2 a%e is an explanatory diagram of the operation of a conventional heat pump water heating system, and Fig. 3 is a diagram showing the water temperature at the inlet of the heating heat exchanger and the required heating. The capacity relationship diagram, FIG. 4A to 4E, is an explanatory diagram of the operation of the heat pump water heater according to an embodiment of the present invention. 1.-fist--heat pump heating unit, 2...φ
・Φ Compressor, 3... Heating heat exchanger, 4...
... Throttle mechanism, 6... Heat source side heat exchanger, 6...
... Hot water tank, 7, 7'-... Gray water piping, 9...
e...Circulation pump, 19...Heat source enthalpy sensor,
2o... River heating heating heat exchanger sensor, 21... River... Control circuit. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 2 Figure 3 Figure 4 THs H

Claims (1)

[Claims] (1) Water is circulated between a heat pump cycle heating unit consisting of a capacity control variable compressor, a heat source side heat exchanger, a heating heat exchanger, and a throttle mechanism connected through an annular refrigerant piping line and a hot water storage tank via a circulation pump. The heat source is connected by a pipe and the capacity of the compressor is controlled by signals from the heat source enthalpy and the water temperature at the inlet of the heating heat exchanger. The heat pump water heating device according to claim 1, wherein the rotation speed of the compressor is increased as the temperature of the water at the inlet of the heater becomes lower. Claim 1 configured to hold at a set value
The heat pump water heating device described in Section 1.