JPS6334375B2 - - Google Patents

Abstract

1. A method of operating a refrigerator in which in each case, the duration of a specific useful operation of the refrigerator which results in the frosting-up of its evaporator, is determined by the time of a defrosting process which precedes the useful operation in question and a defrosting process which follows the useful operation, characterised by the combination of the following features : 1.1 the refrigerator is operated as a heat pump ; 1.2 a defrosting process is initiated only when the instantaneous value of one of the state variables of the refrigerating agent in the evaporator, either the pressure or the temperature, falls below a lower limiting value ; 1.3 when the lower limiting value of the state variable is reached, the useful operation is interrupted, a defrosting process is initiated, and a first timing procedure (t) is commenced ; 1.4 as soon as the state variable has risen to an upper value during the defrosting process, the defrosting process is terminated, the refrigerator is switched to useful operation, and the first timekeeping procedure is terminated and the result thereof is stored ; 1.5 the useful operation is continued if, after a stipulated basic time (tG ), the state variable still lies below the lower limiting value ; 1.6 the useful operation is interrupted again and a defrosting process is initiated if, after the expiry of the basic time (tG ), the instantaneous value of the state variable is equal to or less than the lower limiting value, and at the beginning of the defrosting process which follows the useful operation, a second timing procedure (t) is commenced ; 1.7 on the termination of the last defrosting process to have been executed (which termination takes place when the upper limiting value of the state variable is reached), the second timing procedure (t) is likewise terminated and the result of this timing procedure is stored ; and 1.8 all the succeeding useful operation times are in each case determined by the basic time (tG ) and a correcting value (Kw ) which is added to this basic time and which is formed from the stored last-but-one timing value minus the stored last timing value and from a constant (k) which serves as amplification factor.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides that the heating operation of a heat pump and the defrosting of its evaporator are performed depending on time and the instantaneous value of the state quantity of the refrigerant present in the evaporator of the heat pump. This paper relates to a defrosting method for heat pumps.

Such a method of defrosting a heat pump has already been proposed. In this known defrosting method, the evaporator of a heat pump is defrosted if the evaporation pressure of the refrigerant governing the evaporator drops to a first set value. However, the heating operation of the heat pump continues if, after defrosting, the evaporation pressure is stopped at least twice within a set time to reach the first set value. When the evaporation pressure reaches a second set value, which is set below the first set value, a new defrosting is carried out.

In already known defrosting methods, the outside temperature (at least +5°C to -
5° C.), the operating time of the heat pump is summed. After reaching the set time, the heating operation of the heat pump is stopped, and the evaporator is e.g.
Defrost occurs within 30 minutes by switching the refrigerant circuit.
After the defrosting time has elapsed, the heating operation is restarted, the operating time is newly totaled, and the same process is repeated. Defrosting takes place in this case depending on the outside temperature, regardless of whether the evaporator is iced or not. Such a defrosting method reduces the annual workload of the heat pump. This is because the heating operation is also occasionally stopped when no icing occurs and available heat is available.

The object of the invention is to further improve and improve a defrosting method of the type mentioned at the outset.

Such an object is achieved according to the invention by the method defined in claim 1.

According to the invention, the advantage is obtained that defrosting is limited to the extent absolutely necessary for the benefit of the heating operation of the heat pump.

According to an advantageous embodiment of the invention, instead of the selected state variable of the refrigerant in the evaporator of the heat pump, the outside air temperature is selected as the state variable for starting defrosting.

Next, an embodiment of the present invention will be described based on a schematic diagram showing the temporal progression of heating operation time and defrosting time.

In the drawings, the boxes shown to the right of the center line M indicate the heating operation time, while the boxes shown to the left of the center line M indicate the defrosting time.

In the heat pump defrosting method described in detail below, the heating operation of the heat pump and the defrosting of its evaporator depend on time and the instantaneous value of the state quantity of the refrigerant present in the evaporator of the heat pump. It is done dependently. Evaporation pressure or evaporation temperature is used as the state quantity. Note that it is also possible to use the outside air temperature as the state quantity. The instantaneous values of the selected state variables are not shown in the drawing. However, the starting point is that the instantaneous value of the selected state variable decreases with increasing degree of icing on the evaporator and increases with decreasing degree of icing on the evaporator.

When using evaporation pressure or evaporation temperature as a state quantity, as icing increases, the heat supply to the refrigerant is reduced, and therefore the evaporation temperature and evaporation pressure are lowered. On the contrary, with a reduction in icing, the heat supply to the refrigerant is increased and thus the evaporation temperature as well as the evaporation pressure are increased.

When the selected state variable reaches a lower limit value, for example an evaporation temperature of -8 °C or an outside air temperature of 6 °C, the heat pump is switched from heating operation to defrosting in the position indicated by number 1 in the time diagram and the The first required time (Zeitnahme) t ₁ is started. Defrosting can be accomplished in any manner, such as by spraying the evaporator with salt water, switching the refrigerant circuit, or some other method.

During the defrosting period, the state quantity reaches the upper limit, for example +20℃
As soon as the evaporation temperature reaches , the heat pump is switched from defrosting to heating operation in position 2 of the time diagram. Furthermore, at the same time, the first required time t ₁ ends, and the result of this required time is held.

If the state quantity is still equal to or higher than the lower limit after a certain basic time _tG has elapsed, for example, 60 minutes, the heating operation is further continued.

After the basic time t _G has elapsed, the heating operation is interrupted and the switch to defrosting is performed only when the instantaneous value of the state variable becomes equal to or lower than the lower limit value. Simultaneously with the changeover from heating operation to defrosting, which takes place in position 3 of the time diagram, the second time period t ₂ begins.

When the state quantity reaches the upper limit value again during the defrosting period, the defrosting and the second required time t ₂ end, and the result of this second required time t ₂ is retained (as shown in the time schematic diagram). position 4).

The total operating time t of the next heating operation of the heat pump is then determined by the basic time t _G and the correction K _W added to this basic time t _G , and this correction value is equal to the required time ( In other words, it is formed by multiplying the value obtained by subtracting the previous time (that is, the second time t ₂ ) from the first time t ₁ ) and a constant coefficient K. That is, the total operating time t is given by the following equation.

t=t _G +K _w K _w =K (t ₁ −t ₂ ) By taking such measures, according to the present invention, the following occurs.

If the value of the previous required time t ₂ is larger than the value of the required time t ₁ before the previous one, that is, the previous defrosting time (i.e. the second defrosting time) is longer than the previous defrosting time (i.e. the first defrosting time). (defrosting time), the correction value K _w becomes negative, and the next heating operation time that occurs after the previous defrosting time is the basic time.
t shorter than _G.

On the contrary, if the value of the previous duration t ₂ is smaller than the value of the previous duration t ₁ , i.e. the previous defrosting time is smaller than the previous defrosting time due to relatively slight icing. If it is short, the correction value K _w will be positive. The next heating operation time that follows the previous defrosting time will in this case be longer than the basic time _tG .

[Brief explanation of the drawing]

The figure is a schematic diagram showing the temporal elapse of heating operation time and defrosting time for explaining one embodiment of the present invention. M... Center line, t, t ₁ , t ₂ ... Required time, t _G ...
...Basic time.

Claims (1)

[Claims] 1. A heat pump in which the heating operation of the heat pump and the defrosting of its evaporator are dependent on time and the instantaneous value of the state quantity of the refrigerant present in the evaporator of the heat pump. In the defrosting method, (a) when the state quantity reaches a lower limit value, the heat pump is switched to defrosting, and the first required time is started, and (b) the state is maintained during the defrosting period. As soon as the amount rises to the upper limit value, the heat pump is switched from defrosting to heating operation, and at the same time the first time period ends and the result of this first time period is retained; (c) If the state quantity is still equal to or higher than the lower limit value even after a certain basic time has elapsed, the heating operation is continued, and (d) the instantaneous value of the state quantity becomes the lower limit value after the elapse of the basic time. If it is equal or lower, the heating operation is interrupted anew and the evaporator is defrosted, and a second time period is started with the start of a new defrost; (c) the state quantity is When the upper limit is reached, the new defrosting ends, the second required time also ends, and the result of the second required time is held; (f) the next time of the heating operation; The total driving time is determined by the basic time and a correction value added to the basic time, and the correction value is formed from a value obtained by subtracting the previous time from the previous time and a constant coefficient. A method for defrosting a heat pump, characterized by: 2. The heat pump according to claim 1, wherein instead of the selected state quantity of the refrigerant in the evaporator of the heat pump, outside air temperature is selected as the state quantity for starting defrosting. Defrosting method.