JPH01134170A - Safety device for refrigeration cycle - Google Patents

Abstract

PURPOSE: To detect low efficiency state quickly and to enhance reliability by an arrangement wherein supercooling of refrigerant is determined based on signals from refrigerant temperature and pressure detectors disposed at the outlet of a condenser and start/stop of a compressor is controlled. CONSTITUTION: A refrigerant temperature sensor, i.e., a thermistor 10, and refrigerant pressure sensor, i.e., a pressure transducer 11, are disposed in the vicinity of the outlet of a condenser 2 and a controller 12 receiving electric signals therefrom controls start/stop of the compressor 1, a circulation pump 5 and an indicating means, i.e., alarm lamps 13, 14. Since supercooling is detected by means of the thermistor 10, the pressure transducer 11, and the controller 12, the control range can be made very wide as compared with conventional control base only on the temperature. Since low efficiency state can be detected quickly, electric power is used effectively while shortening the abnormal operation time of the compressor 1 and the reliability can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a safety device for a refrigeration cycle used in an air conditioner or a water heater.

2. Description of the Related Art In recent years, a large number of products using refrigeration cycles, such as air conditioners and water heaters, have been commercialized.

Hereinafter, a conventional refrigeration cycle safety device will be explained using a solar water heater shown in FIG.

In the figure, compressor 1. Condenser 2. g Expansion valve as pressure machine groove 3. The evaporators 4 are successively connected to form a refrigeration cycle. The condenser 2 is a water-cooled type, and a circulation pump 5 circulates water from a hot water storage tank of 6 yen to collect heat. Furthermore, fluorocarbon gas is circulated as a refrigerant on the refrigeration cycle side.

As a safety device, a temperature detector 7 is attached to the discharge part of the compressor 1, and a controller 8 that detects the temperature of the discharged refrigerant and determines abnormality controls the start/stop of the compressor 1 and the circulation pump 5.

The operation of the thus configured discharge refrigerant temperature detection method will be described below.

During normal operation, the discharge refrigerant temperature of the compressor 1 is 20 to 30°C higher than the condensing temperature, that is, the water temperature at the water side outlet 9 of the condenser 2, and rises to about 85°C compared to the boiling temperature of 55°C. There is.

If there is a shortage of gas due to a gas leak, etc., the load on the compressor 1 will increase, causing the evaporation pressure to drop, which will increase heat generation in the compressor and reduce the discharge refrigerant temperature to 100%.
An abnormal condition exceeding ``C'' occurs.

This temperature was detected by a temperature detector 7, and a controller 8 controlled to stop the compressor 1 when the temperature reached a set temperature (for example, 100° C.) or lower.

Problems to be Solved by the Invention However, the configuration of the safety device for the refrigeration cycle as described above has the following problems.

(1) This is a safety device only for the lowest temperature of the refrigerant discharged from the compressor.While the condensing temperature is low, even if there is a lack of gas, it cannot be detected if the temperature is below the set temperature, so the capacity decreases due to a lack of gas. This inefficient operating condition continues for a considerable period of time, resulting in wasted electricity costs.

(2) This is a control method for the maximum temperature of the refrigerant discharged from the compressor.The set temperature of the temperature detector is set so that the boiling water is close to 55℃ in winter and low outside temperatures when the load is at its maximum. If set, it will not be detected unless there is a considerable refrigerant shortage during seasons such as summer when the load is low.

(3) When overfilling with refrigerant, the temperature of the refrigerant discharged from the compressor hardly changes from normal, so when the amount of refrigerant is too large, it is impossible to detect the degree of supercooling.

In view of the above problems, the present invention provides a refrigeration cycle safety device that can constantly detect abnormalities such as insufficient cooling and overfilling of refrigerant, regardless of the season or water temperature.

Means for Solving the Problems In order to solve the above problems, the refrigeration cycle safety device of the present invention is provided with a refrigerant temperature detector and a pressure detector at the condenser outlet, and detects the refrigerant temperature by signals from these two. The system is equipped with a controller that calculates and determines the degree of subcooling and controls the start and stop of the compressor.

Operation In the above configuration, the degree of supercooling during operation of the compressor is detected by the temperature sensor and the pressure sensor, and the start/stop of the compressor is controlled.

EXAMPLE Hereinafter, a safety device for a refrigeration cycle according to an example of the present invention will be described with reference to the drawings.

FIG. 1 is an overall system diagram of a safety device for a refrigeration cycle according to an embodiment of the present invention.

Since the refrigeration cycle has the same configuration as that of the conventional example, the same components as those of the conventional example are given the same reference numerals, and their explanations will be omitted.

A thermistor 10 as a refrigerant temperature detector is provided near the outlet of the condenser 2, and a pressure quadrangle juicer 11 as a refrigerant pressure detector is provided.

A controller 12 receives both electrical signals and calculates them.
Compressor 1. Circulation pump 5. It controls turning on and off of warning lamps 13 and 14 as display means.

FIG. 2 shows a partial cross section showing the details of the detection section.

A thermistor 10 is fixed to the pipe wall of a pipe 15 at the outlet of the condenser 2 with a fixing band 16, and a pressure-quadrant juicer 11 is attached by screwing into a round connecting pipe 17. Each signal is connected to the controller 12 by wires 18, 19.

The operation of the single refrigeration cycle safety device constructed as described above will be explained below with reference to FIGS. 3, 4, and 5.

First, FIG. 3 is a temperature/pressure characteristic diagram of a refrigerant, and line A shows the temperature/pressure characteristic of the refrigerant used in a saturated state, which is determined as a physical property value depending on the type of refrigerant. Approximately 3 from this line
``The first setting value, which is lower by the degree of supercooling of C, is set to line B, and about 1
Line C shows a second set value that is lower by the degree of supercooling of 0'(:l'.

Next, how a change in the amount of refrigerant in the refrigeration cycle affects this will be explained using FIG. 4.

FIG. 4 is a Mollier diagram of fluorocarbon gas, in which the state of the condenser outlet in a normal cycle state is b1, the similar state in a cycle state when gas is insufficient, and a1 is the state when overfilled with gas is C.

In other words, the operating state with an appropriate amount of refrigerant that is in the liquid region below the saturation state line and has an appropriate degree of supercooling is b, and as the gas becomes insufficient due to gas leaks etc., the degree of supercooling gradually decreases. When the degree of supercooling reaches the saturation state line op, the degree of supercooling becomes 0 (zero), and when it decreases further, the refrigerant at the outlet of the condenser 2 is not in a liquid state but in a two-phase state of liquid and gas. This point is a. In FIG. 3, this state is a point a' on the saturation state line A where the degree of supercooling is 0 (zero). In other words, within the two-phase region, the state only changes from liquid to gas while the degree of supercooling remains 0 (zero).

Then, when additional refrigerant is charged for inspection or the like, the temperature changes from point 1 to point C, and the degree of supercooling increases. When the gas is overfilled, the degree of supercooling becomes higher than the second set value, the condensing pressure increases, and the current value of the compressor 1 increases significantly. This n is point C, which is point C' in FIG.

Next, the control operation of the refrigeration cycle safety device of the present invention will be explained in the fifth step.
This will be explained using the flowchart shown in the figure.

First, start the compressor 1 and the circulation pump 5, and wait until the refrigeration cycle becomes stable (usually about 30 minutes).
The control operation is delayed for a certain period of time in order to accurately grasp the state. After that, when the state becomes stable, thermistor 1
0 and the refrigerant temperature "I" by the pressure cadence juicer 11.
tMeasure the pressure P1. Then, the degree of supercooling T is calculated from this signal using the following equation.

T=t2-tl Here, t2 is the saturation temperature at the pressure of Pl in the saturated state of the refrigerant, and is stored in advance in the controller 12.

As a result, if T is the first set value, then the point a' in FIG. 3 is reached, and the compressor 1 and circulation pump 5 are stopped because the capacity is reduced due to lack of refrigerant and the efficiency is poor. Then, the warning lamp 13 is turned on as an abnormality indication to notify the user of the refrigerant shortage.

If T > 2nd set value, then the point will be C' in Figure 3, and the condensing pressure will drop due to overfilling of gas, causing a failure of the compressor 1, so the compressor 1 and circulation pump 5 stop. Similarly, the alarm lamp 14 is turned on to notify the user of refrigerant overfill.

Effects of the Invention As is clear from the above description of the embodiments, the refrigeration cycle safety device of the present invention detects the degree of subcooling using a refrigerant temperature sensor, a pressure sensor, and a controller thereof. Even when the condensing temperature is low, the state of the refrigerant can be ascertained.
Compared to conventional control based only on temperature, a much wider range of control is possible, allowing for early detection of inefficient conditions, eliminating wasted electricity, and reducing the amount of time the compressor is used due to abnormal conditions. performance is significantly improved.

[Brief explanation of the drawing]

Fig. 1 is an overall system diagram showing a safety device for a refrigeration cycle according to an embodiment of the present invention, Fig. 2 is a partial sectional view showing the main parts of Fig. 1, and Fig. 3 shows the relationship between refrigerant temperature and pressure. FIG. 4 is a characteristic diagram showing the relationship between refrigerant enthalpy and pressure, FIG. 5 is a flowchart showing the control operation of the present invention,
FIG. 6 is an overall system diagram showing a conventional refrigeration cycle safety device. 1... Compressor, 2... Condenser, 3...
...Expansion valve, 4...Evaporation 6, to...
...Thermistor, 11... Pressure cadence juicer, 12... Controller. Name of agent: Patent attorney Toshio Nakao and 1 other person1-
--) E Bribery number 4 --- figure

Claims (4)

[Claims] (1) A refrigerant temperature sensor and a refrigerant pressure sensor are installed near the outlet of the condenser of a refrigeration cycle in which a compressor, a condenser, a pressure reduction mechanism, and an evaporator are connected in order to circulate the refrigerant, and these temperature sensors are installed. 1. A safety device for a refrigeration cycle, characterized in that starting and stopping of the compressor is controlled by a controller that calculates and determines the degree of subcooling of the refrigerant based on signals from a pressure sensor and a pressure sensor. (2) The controller starts calculating the degree of supercooling after a certain period of time has elapsed after the compressor starts.
Refrigeration cycle safety devices as described in section. (3) The safety device for a refrigeration cycle according to claim 1, further comprising display means for displaying the abnormality by means of a lamp or the like when the controller determines that there is an abnormality in the degree of subcooling. (4) The controller has a first set value and a second set value for the degree of supercooling, and when it detects a value lower than the first set value, it determines that there is a gas shortage, stops the compressor, and displays the When a shortage is displayed and a value higher than the second set value is detected,
4. The safety device for a refrigeration cycle according to claim 3, wherein the refrigerant cycle safety device determines that gas is overfilled, stops the compressor, and displays the overfilling of the refrigerant using the display means.