JP5068354B2 - Refrigeration equipment - Google Patents

Description

  The present invention increases the density of frost generated on the surface of the evaporator fin by controlling the refrigerant temperature in an evaporator such as a refrigeration apparatus installed in a refrigerated warehouse, resulting in the frost height direction. It is possible to suppress the growth of water and extend the cooling operation time.

  The refrigeration apparatus includes a compressor, a condenser, expansion means, and an evaporator, and a refrigerant is filled in the refrigeration cycle circuit. The refrigerant compressed by the compressor becomes a high-temperature and high-pressure gas refrigerant and is sent to the condenser. The refrigerant that has flowed into the condenser is liquefied by releasing heat into the air. The liquefied refrigerant is decompressed by the expansion means to be in a gas-liquid two-phase state, and is gasified by absorbing heat from ambient air in the evaporator and returns to the compressor.

  In a refrigerated warehouse, the inside of the warehouse must be controlled to a temperature range lower than 10 ° C. Since the refrigerant evaporating temperature at that time is lower than 0 ° C., frost is generated on the evaporator fin surface. When frost is generated, the cooling capacity is reduced due to a decrease in the air volume and an increase in thermal resistance. Therefore, a defrosting operation that periodically removes frost is required.

  Since the defrosting operation is performed by stopping the cooling operation and heating with a heater installed in the evaporator and the drain pan, problems such as an increase in internal temperature and an increase in power consumption have occurred.

  Therefore, the intake air temperature and humidity of the evaporator were measured, the lower limit value of the evaporation temperature corresponding to each air condition determined from the measured outside air temperature and humidity was set in advance, and the actual evaporation temperature was set in advance. Some control frost formation by controlling the temperature to be equal to or higher than the evaporation temperature at which no frost formation occurs. (For example, refer to Patent Document 1).

  Also, during pull-down operation where the internal temperature is higher than the set temperature, such as at the start of operation, the evaporating temperature is increased to suppress the expansion of the frost area and the frost area during pull-down operation is suppressed. There is a thing which suppresses the fall of the cooling capacity resulting from expansion. (For example, refer to Patent Document 2).

Japanese Patent Publication No. 61-27665 JP 2007-298218 A

  However, for those that operate above the evaporating temperature that does not form frost, which is determined from the intake air temperature and humidity, there is a problem that the cooling capacity is insufficient, the internal temperature does not reach the set temperature, and the quality of the goods received decreases. is there. In order to keep the inside temperature at the set temperature, the evaporation temperature must be lowered to some extent, and therefore frosting of the evaporator cannot be avoided.

  Also, focusing on only when pulling down, control the evaporation temperature to be equal to or higher than a predetermined value until the internal temperature reaches the set temperature range when pulling down. The expansion of the frost formation area becomes a problem. Since the operation time after the pull-down is longer than the actual pull-down, it is also important to suppress the frosting area expansion after the pull-down.

  The present invention has been made in consideration of the above-mentioned problems, and detects the frosting state of the evaporator, and based on the detected frosting state, the range in which the cooling does not become insufficient from the pull-down to the defrosting operation. By increasing the evaporation temperature, the density of frost generated on the fin surface of the evaporator is increased, thereby suppressing frost growth and extending the cooling operation time. .

  The refrigerating apparatus of the present invention is a refrigerating apparatus having a refrigerant circuit including a compressor, a condenser, an expansion means, and an evaporator. Evaporation temperature detecting means for detecting the evaporation temperature of the evaporator; Frosting detection means for adjusting the rotation speed of the compressor, and determining the evaporation temperature that does not cause a lack of cooling capacity according to the detection result of the frosting detection means. The rotation speed of the compressor is adjusted by the compressor rotation speed adjusting means so that the evaporating temperature at which the detected value is determined does not cause the cooling capacity shortage.

  According to the refrigeration apparatus of the present invention, an evaporation temperature that does not cause insufficient cooling capacity is determined according to the detection result of the frost detection means, and the detected value of the evaporation temperature detecting means becomes an evaporation temperature that does not cause insufficient cooling capacity. Then, the rotation speed of the compressor is adjusted by the compressor rotation speed adjusting means. Thereby, the refrigeration apparatus can suppress the growth of frost by densifying the frost generated on the surface of the evaporator without falling under cooling. Therefore, in the cooling operation, blockage due to frost between the fins constituting the evaporator is delayed, and the cooling operation time is extended. As a result, the number of times of defrosting is reduced, and the rise in the internal temperature and the increase in power consumption are suppressed.

1 is a schematic diagram of a refrigeration apparatus according to Embodiment 1 of the present invention. FIG. 2 is a schematic diagram of frost formation detection means according to Embodiment 1 of the present invention. FIG. 5 is a diagram showing a change over time in cooling capacity according to Embodiment 1 of the present invention. FIG. 3 is a schematic diagram showing a positional relationship between an evaporator and frost detection means according to Embodiment 1 of the present invention. FIG. 5 is a schematic diagram showing the amount of reflected light when no frost is formed and when frost is formed in the frost detection means according to Embodiment 1 of the present invention. FIG. 3 is a diagram showing the relationship between the frost layer thickness and the light amount in the frost detection means of Embodiment 1 of the present invention, and the relationship between the light amount and the output of the frost detection means. FIG. 2 is an air diagram illustrating Embodiment 1 of the present invention. FIG. 6 is a diagram comparing the relationship between the frost height generated when operating at a low evaporation temperature and a high evaporation temperature and the operation time, and the time when the defrost operation is started, illustrating Embodiment 1 of the present invention. FIG. 3 is a control flow diagram of Embodiment 1 of the present invention. FIG. 3 is a diagram showing a fin blocking rate and an air flow ratio of the evaporator according to Embodiment 1 of the present invention. FIG. 5 is a schematic diagram of a refrigeration apparatus according to Embodiment 2 of the present invention. FIG. 6 is a control flow diagram of Embodiment 2 of the present invention. It is a control flow figure following Drawing 12A. FIG. 3 is a diagram showing the position of frost formation detection means in the evaporators of Embodiments 1 and 2 of the present invention. FIG. 4 is a diagram showing the position of frost formation detection means, air flow, and refrigerant flow in the evaporators of Embodiments 1 and 2 of the present invention. FIG. 3 is a diagram showing the position of frost formation detection means in the evaporators of Embodiments 1 and 2 of the present invention. FIG. 6 is a schematic diagram showing another configuration of the refrigeration apparatus according to Embodiments 1 and 2 of the present invention. FIG. 5 is a diagram showing compressor operation and evaporation temperature behavior according to Embodiments 1 and 2 of the present invention. FIG. 5 is a diagram illustrating compressor operations according to Embodiments 1 and 2 of the present invention.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram of a refrigeration apparatus according to an embodiment of the present invention. The refrigeration apparatus 1 includes a compressor 2, a condenser 3, an expansion means 4 such as an expansion valve, a refrigeration cycle circuit (refrigerant circuit) composed of an evaporator 5, etc., a condenser fan 6, and an evaporator fan 7. The evaporator 5 and the evaporator fan 7 are installed inside the freezer 12. In addition, the refrigeration apparatus 1 includes a compressor rotation speed detection means 8, a compressor rotation speed adjustment means 9, an evaporation temperature detection means 10, an internal temperature detection means 11, and a frost detection means for detecting the amount of frost formation on the evaporator 5. 21. The compressor rotational speed detecting means 8, the evaporation temperature detecting means 10, and the internal temperature detecting means 11 are composed of sensors for measuring them. The compressor rotation speed adjusting means 9 can be constituted by an electronic circuit or a microcomputer.

The frost detection means 21 includes, for example, a light emitting element 21a composed of a light emitting diode (LED) capable of irradiating light having an infrared wavelength as shown in FIG. 2, and a light receiving element 21b composed of a photodiode (PD). The control device 22 is connected to them. Under the control of the control device 22, the light emitted from the light emitting element 21a is reflected by the fin 5a constituting the evaporator 5 and returned to the light receiving element 21b. The amount of frost formation on the fin 5a is detected by outputting a current or the like according to the amount of light that is returned.
The frost detection means 21 uses the outside air temperature and the evaporation temperature, uses the capacitance between the fins or between the fins and the electrode, uses the radiation temperature of the fins, etc. Other frost detection means may be employed.

  Next, the operation will be described. In the refrigeration apparatus 1 shown in FIG. 1, the refrigerant compressed by the compressor 2 becomes a high-temperature and high-pressure gas refrigerant and is sent to the condenser 3. The refrigerant flowing into the condenser 3 is liquefied by releasing heat to the air introduced by the condenser fan 6. The liquefied refrigerant flows into the expansion means 4. The liquid refrigerant is decompressed by the expansion means 4 to become a gas-liquid two-phase flow state, sent to the evaporator 5, and gasified by absorbing heat from the air introduced by the evaporator fan 7, to the compressor 2. Returned.

  When the evaporation temperature of the refrigerant in the evaporator 5 is 0 ° C. or lower, moisture present in the air adheres to the evaporator 5 and accumulates as frost. The amount of deposition increases with time. As a result, as shown in FIG. 3, the cooling capacity of the evaporator 5 decreases with time due to increased thermal resistance and ventilation resistance due to frost adhering to the fins 5a constituting the evaporator 5. Therefore, for example, as shown in the schematic view of the evaporator of FIG. 4 (b) as seen from the side, a heater 23 is provided in the evaporator 5 of the cooling device used in the freezing / refrigeration warehouse, and the heat of the heater 23 is used. The frost can be melted by the defrosting operation. Further, at the time of defrosting, the drain pan 24, which is a tray for drain water, is heated by the drain pan heater 25 so that the drain water does not freeze again.

  Normally, the refrigeration unit operates at a lower evaporation temperature, stops the compressor operation (thermo-off) when the internal temperature reaches the set temperature, and resumes the compressor operation when the set temperature rises above a certain value. (Thermo-on) keeps the internal temperature at the set temperature. At this time, if the evaporation temperature is lower than necessary, low-density frost grows and frost tends to grow in the stacking height direction, and the closure between the fins of the evaporator 5 (simply referred to as fin closure) is accelerated. Will end up.

  The fact that the fins are closed earlier means that the capacity reduction of the evaporator 5 is accelerated and the defrosting operation interval is shortened. Therefore, in order to suppress the rise in the internal temperature and the increase in power consumption due to the defrosting operation, it is necessary to delay the growth of the frost in the stacking height direction, delay the fin blockage, and lengthen the defrosting operation interval.

  The positional relationship between the evaporator 5 and the frost detection means 21 is shown in a schematic view of the evaporator of FIG. 4 (a) and FIG. 5 as viewed from above. In this case, when frost 40 adheres to fin 5a of evaporator 5 as shown in FIG. 5, light emitted from light emitting element 21a is reflected by the frost. As shown in the upper part of FIG. 6, the amount of reflected light increases in amount of light returning to the light receiving element 21b in accordance with the frost layer thickness. Further, as shown in the lower part of FIG. 6, the output of the frost detection means 21 (for example, the output value converted into current) also changes according to the amount of light returning to the light receiving element 21b. The thickness of the frost generated on the fin 5a can be detected.

  On the other hand, the density of the frost generated on the fins 5a of the evaporator 5 varies depending on conditions. For example, under the same air temperature and humidity conditions, the higher the surface temperature of the fin 5a, that is, the higher the evaporation temperature of the refrigerant in the evaporator 5, the higher the density frost is generated, and the lower the evaporation temperature, the lower the density frost is generated. . This will be described with reference to the air diagram of FIG. As shown in FIG. 7, when the evaporation temperature ET, the internal temperature (air temperature) Ta, and the air dew point temperature Tdp, the smaller the (Tdp-ET) / (Ta-ET), the higher the density of the generated frost. Become. The density of frost is also related to the temperature boundary layer thickness. The higher the temperature boundary layer thickness, the lower the density, and the thinner the temperature boundary layer thickness, the higher the density, but here the temperature boundary layer thickness is constant. I think.

  In other words, under the same air temperature and humidity conditions, by operating at a higher evaporation temperature than at a low evaporation temperature, it is possible to grow high-density frost and suppress the growth of frost in the stacking height direction. FIG. 8 is a diagram showing the relationship between the passage of time and the height of the frost generated on the fins of the evaporator in terms of the relationship between the two evaporation temperatures (low evaporation temperature and high evaporation temperature) of the refrigerant. From FIG. 8, it is understood that the growth in the frost height direction is delayed at the high evaporation temperature compared to the low evaporation temperature, and the defrosting operation interval can be extended. FIG. 8 also shows that the defrosting operation start determination can be made based on the frost height detected by the frost detection means 21.

  However, simply increasing the evaporation temperature may cause insufficient cooling capacity and increase the internal temperature. Further, as the frosting progresses, the air volume decreases and the thermal resistance increases, and the cooling capacity decreases even at the same evaporation temperature. Therefore, it is difficult to determine the evaporation temperature according to the frosting state.

  Therefore, in the first embodiment, the frost detection means 21 for detecting the amount of frost formation of the evaporator 5 is provided, and the evaporation is performed within a range in which the cooling capacity is not insufficient based on the frost layer thickness detected by the frost detection means 21. This makes it possible to control the highest temperature. The details of the control will be described below.

  FIG. 9 shows an example of a control flow of the refrigeration apparatus according to the first embodiment. After starting the cooling operation, in S-1, the operation is performed at an arbitrary evaporation temperature ET. The evaporation temperature ET is adjusted by changing the rotational speed of the compressor 2 by the compressor rotational speed adjusting means 9. In S-2, it is determined whether or not the internal temperature detected by the internal temperature detection means 11 has reached the set temperature. If it is determined in S-2 that the internal temperature has reached the set temperature, an evaporation temperature ET that does not perform thermo-off (thermo OFF) is determined in S-3.

  The determination of the evaporation temperature ET that does not perform thermo-off is performed as follows, for example. When the compressor 2 is thermo-off after being thermo-off, the evaporating temperature ET is increased by a predetermined value from the evaporating temperature ET before thermo-off. By repeating this operation, it is possible to determine the evaporation temperature ET (particularly a value near its limit) that does not thermo-off. The predetermined value is 1 ° C., for example.

  When the evaporation temperature ET that does not thermo-off is determined in S-3 and the operation is continued while adjusting the compressor frequency so as to maintain the evaporation temperature ET, frosting on the fin 5a progresses and the air volume decreases. And cooling capacity decreases due to increased thermal resistance. When the cooling capacity decreases, it is necessary to lower the evaporation temperature ET to increase the capacity.

  Therefore, in S-4, it is determined whether the frost layer thickness of the fin 5a of the evaporator 5 detected by the frost detection means 21 is equal to or greater than a predetermined thickness t_f0. Then, the capacity drop is predicted according to the frost layer thickness, and the evaporation temperature ET is determined.

  Here, a method of determining the evaporation temperature ET according to the frost layer thickness will be described. Va_i for non-frosting (initial stage of operation) in S-3, Va_i for evaporation temperature, Ta_i for chamber temperature, Va for S-5 (current), ET for evaporation temperature to be determined, and chamber interior The temperature is Ta, and the frost layer thickness detected by the frost detection means 21 is t_f.

  The capacity Q_i at the start of operation in S-3 may be considered to hold the relationship of the following formula (1), where ρa is the air density.

        Q_i = Va_i x (Ta_i-ET_i) x rho (1)

  Further, it may be considered that the required cooling capacity in S-5 is substantially equal to the required cooling capacity Q_i in S-3, and the following relationship is established.

        Q_i = Va × (Ta-ET) × ρa (2)

  The air density ρa may be considered constant, and the following equation (3) is established from the above two equations.

        Va_i x (Ta_i-ET_i) = Va x (Ta-ET) (3)

    From the above, the evaporation temperature ET determined in S-5 is obtained by the following equation (4).

        ET = (Va_i / Va) x (ET_i-Ta_i) + Ta (4)

  Here, the initial air volume Va_i is a value unique to the device, ET_i is determined in S-3, and the internal temperature Ta_i, Ta is a value detected by the internal temperature detection means 11, so the evaporation temperature ET is determined. The unknown value is the current air volume Va.

  The current air volume Va is estimated from the frost layer thickness tf detected by the frost detection means 21 as follows.

  First, the blockage rate α expressed by the following equation (5) is calculated from the frost layer thickness tf. Here, FP represents the pitch between the fins 5a of the evaporator 5, and FT represents the plate thickness of the fins 5a.

        α = 2 × tf / (FP-FT) (5)

  The relationship between the current air volume ratio (air volume ratio) β to the air volume during non-frosting and the blockage rate α is an upwardly convex curve as shown in FIG. This curve can be approximated by a simple equation such as β = −α ^ 2 + 1, and the current air flow ratio β can be calculated by calculating the blockage rate α from the frost layer thickness tf. The approximate expression described above is not limited to the one shown here, but an approximate expression that best suits the device, such as β = −α ^ 4 + 1, may be used.

  Once the air volume ratio β is calculated, the current air volume Va is derived by multiplying the initial air volume Va_i by the air volume ratio β, and the evaporation temperature ET corresponding to the detected frost layer thickness is determined by the above equation (4). Is done.

In S-6, it is determined whether or not the frost generated on the fin 5a by the frost detection means 21 has a frost layer thickness that needs to be defrosted. When the defrosting operation is completed, the process returns to S-1. On the other hand, if it is determined that defrosting is not yet required, the process returns to S-5, and the cooling operation is continued while determining the evaporation temperature again.
In S-6, since the start of the defrosting operation is determined by the frost detection means 21 that directly detects the frost formation state, useless defrosting operation such as defrosting even though the frost has not been removed is eliminated. it can.

  By controlling the first embodiment, it is possible to increase the evaporation temperature within a range that does not cause insufficient cooling from the start of the cooling operation to the start of the defrosting operation, thereby increasing the frost layer density and suppressing the growth in the frost height direction. It becomes possible. Thereby, the defrosting operation interval is extended (that is, the cooling operation time is extended), and it is possible to suppress an increase in the internal temperature and an increase in power consumption due to the defrosting operation.

Embodiment 2. FIG.
In the second embodiment, as shown in FIG. 11, an internal humidity detecting means (sensor) 13 for detecting the internal humidity is added to the configuration of the first embodiment. Therefore, the same parts as those in the first embodiment are omitted.

  As described in FIG. 7, assuming that the evaporation temperature ET, the internal temperature (air temperature) Ta, and the air dew point temperature Tdp, the smaller the (Tdp-ET) / (Ta-ET), the higher the frost density. Further, at the same evaporation temperature ET, the closer the air condition is to a line with 100% relative humidity, the larger the (Tdp-ET) / (Ta-ET) tends to be, and the lower the frost density.

  Such a tendency occurs when stored items are brought into the warehouse at the start of operation, after the completion of the defrosting operation, and the like. In the present embodiment, when the internal humidity detected by the internal humidity detecting means 13 becomes high and (Tdp-ET) / (Ta-ET) increases, first, the evaporation temperature ET is raised. After dehumidifying priority operation, the evaporating temperature ET is lowered and cooling priority operation is performed. By carrying out such an operation, it is possible to increase the density of the generated frost and suppress the growth in the height direction.

  12A and 12B show an example of the control flow of the refrigeration apparatus according to the second embodiment. After starting the cooling operation at an arbitrary evaporation temperature ET, in S-1, the relative humidity RH in the cabinet and the dew point temperature Tdp are calculated from the detection value of the cabinet temperature detection means 11 and the detection value of the cabinet humidity detection means 13. Ask. In S-2, the relative humidity RH is compared with a predetermined value RH0.

  Here, the predetermined value RH0 is, for example, 80% relative humidity, but may be set according to the environment in which the refrigeration apparatus is used.

If the relative humidity RH is determined to be RH0 or higher in S-2, determine the evaporation temperature ET so that (Tdp-ET) / (Ta-ET) is smaller than the predetermined value γ in S-3. Drive. Here, the predetermined value γ can be set according to the use conditions of the refrigeration apparatus, and can be set to γ = 0.7, for example, under the refrigeration conditions. For example, if the air temperature is 0 ° C. and the dew point temperature is −1.4 ° C. (relative humidity 90%), the operation is performed at ET = −5 ° C. for γ to be smaller than 0.7.
If the relative humidity RH is smaller than the predetermined value RH0 in S-2, the process immediately proceeds to S-5.

  Thereafter, in S-4, it is determined whether or not the relative humidity has become lower than RH0. If it is determined that the relative humidity has decreased, the dehumidification priority operation ends, and the process proceeds to S-5 to shift to the cooling priority operation. If the relative humidity is not lower than RH0, the process returns to S-3.

  In S-5, first, operation is performed at an arbitrary evaporation temperature. In S-6, it is determined whether or not the evaporation temperature has reached a set temperature. If it is determined in S-6 that the set temperature has been reached, the evaporation temperature ET that is not thermo-off is determined in S-7 as in S-3 of FIG. If the evaporation temperature has not reached the set temperature, the process returns to S-5.

  In S-8, as in S-4 of FIG. 9 of Embodiment 1, it is determined whether or not the frost layer thickness t_f detected by the frost detection means 21 is greater than or equal to a predetermined thickness t_f0, and the detected frost layer When the thickness t_f is equal to or greater than t_f0, the operation is performed by determining the evaporation temperature ET according to the frost layer thickness in S-9, as in S-5 of FIG. 9 of the first embodiment. If the detected frost layer thickness t_f is less than t_f0, the process proceeds to S-11.

  In S-10, if the amount of frost generated on the fin 5a detected by the frost detection means 21 is determined to be the frost layer thickness that requires defrosting, and if it is determined that defrosting is necessary, When the defrosting operation is completed and the defrosting operation is completed, the process returns to S-1. This determination can be made by comparing the value obtained from the frost detection means 21 with a predetermined value. On the other hand, if it is determined that defrosting is not yet necessary, the process proceeds to S-15.

  In S-11 and S-12, the same processing as S-2 and S-3 is performed. If it is determined in S-11 that the relative humidity RH is less than the predetermined value RH0, the process returns to S-7. On the other hand, if it is determined in S-11 that the relative humidity RH is equal to or higher than RH0, in S-12, the evaporation temperature ET such that (Tdp-ET) / (Ta-ET) is smaller than the predetermined value γ. In S-13, it is determined again whether or not the fins need to be defrosted. When defrosting is necessary, defrosting operation is performed. When defrosting is unnecessary, the same judgment as S-4 is performed in S-14. If it is determined in S-14 that the relative humidity RH is RH0 or higher, the process proceeds to S-7, and if not, the process returns to S-12.

  In S-15 to S-18, as shown in the figure, substantially the same processing as S-11 to S-14 is performed.

  As described above, in S-10, S-13, and S-17, the start of the defrosting operation is determined based on the detection result of the frosting detection means 21 that actually detects the frosting condition. Unnecessary defrosting operations such as defrosting can be eliminated.

  The above control increases the evaporation temperature to increase the density of frost generated on the fins 5a even if the inside of the refrigerator has a high relative humidity and the frost density is low, and the frost stacking height during the cooling operation is increased. Growth in the vertical direction can be suppressed. In addition, it is possible to increase the evaporation temperature within a range that does not cause insufficient cooling from the start of the cooling operation to the start of defrosting, thereby increasing the frost layer density and suppressing the growth in the frost height direction. As a result, the defrosting interval is extended (cooling operation time is extended), and it is possible to suppress an increase in the internal temperature and an increase in power consumption due to the defrosting operation.

  In the first and second embodiments of the present invention, as shown in FIG. 13, it is better to place the frost detection means 21 at a location where the frost amount is the largest. When the amount of frost formation on the windward side increases, it is arranged on the leeward side when the amount of frost formation on the leeward side increases. By installing the frost detection means 21 on the side where the amount of frost formation is large, it becomes possible to estimate the capacity reduction more accurately. Further, at this time, as shown in FIG. 14, the refrigerant inlet is arranged on the side where the amount of frost formation is large, and the refrigerant outlet where the refrigerant temperature is reduced due to pressure loss is arranged on the side where the amount of frost formation is small. When the evaporation temperature on the larger side is increased, the frost density can be increased and the effect is increased.

  In the first and second embodiments of the present invention, as shown in FIG. 15, the frost detection means 21 may be movable so that the frost formation state of the entire evaporator 5 can be detected. By setting it as such a structure, the false detection of a frosting condition reduces also when uneven frosting is carried out.

  In the first and second embodiments of the present invention, as shown in FIG. 16, the expansion means in the refrigerant circuit is an electronic expansion valve 34, and the evaporator outlet temperature detecting means 35 is provided at the outlet of the evaporator 5. It is good. With this configuration, the refrigerant superheat degree (SH) at the outlet of the evaporator 5 can be controlled. In situations where the load is high and the capacity is desired, the target refrigerant superheat degree SH is reduced (for example, 3 [K]) to reduce the cooling capacity. It is good also as control which raises and raises evaporation temperature more. Conversely, when the load is low and the evaporation temperature is sufficiently high, the energy-saving effect may be enhanced as control for increasing the target refrigerant superheat degree SH (for example, 10 [K]) in order to increase the operation efficiency during cooling. .

  Furthermore, in the first and second embodiments of the present invention, the purpose is to increase the frost density by increasing the evaporation temperature. However, in the case of a low load, etc., the minimum rotation speed of the compressor 2 is reduced. Thus, there may be a situation where the evaporation temperature cannot be raised to the determined temperature. In this case, thermo-on and thermo-off (thermo ON / OFF) are repeated. In the case of thermo-on, the compressor rotational speed is rapidly increased, and the evaporation temperature is temporarily lowered as shown in FIG. 17, resulting in a lower frost density. Therefore, the restart of the compressor 2 in the case of repeating the thermo ON / OFF may make the rotational speed increase speed slower than usual as shown in FIG. By doing in this way, it becomes possible to suppress the primary evaporating temperature fall at the time of restart and to grow high-density frost.

  DESCRIPTION OF SYMBOLS 1 Refrigeration apparatus, 2 Compressor, 3 Condenser, 4 Expansion means, 5 Evaporator, 5a Fin, 6 Condenser fan, 7 Evaporator fan, 8 Compressor rotation speed detection means, 9 Compressor rotation speed adjustment means, 10 Evaporation temperature detection means, 11 Inside temperature detection means, 12 Freezer, 13 Inside humidity detection means, 21 Frost detection means, 21a Light emitting element, 21b Light receiving element, 22 Control device, 23 Evaporator heater, 24 Drain pan, 25 Drain pan Heater, 40 frost.

Claims (11)

In a refrigeration apparatus having a refrigerant circuit including a compressor, a condenser, expansion means, and an evaporator,
Evaporation temperature detection means for detecting the evaporation temperature of the evaporator, frost detection means for detecting the amount of frost formation of the evaporator, compressor rotation speed adjustment means for adjusting the rotation speed of the compressor,
According to the detection result of the frost detection means, an evaporation temperature that does not cause insufficient cooling capacity is determined, and the compressor rotation is performed so that the detected value of the evaporation temperature detection means becomes the evaporation temperature that does not cause insufficient cooling capacity. A refrigerating apparatus characterized by adjusting the number of rotations of the compressor by a number adjusting means.   2. An in-chamber temperature detecting means for detecting an in-chamber temperature for performing air conditioning is provided, and the evaporating temperature that does not cause a lack of cooling capacity is determined after the in-chamber temperature reaches a set temperature. The refrigeration apparatus described in 1.   Determination of the evaporation temperature that does not cause a shortage of capacity is the amount of air that passes through the evaporator in the initial stage of operation, the evaporation temperature and the internal temperature, the amount of air that passes through the evaporator when determining the evaporation temperature that does not cause the lack of capacity, The refrigeration apparatus according to claim 1, wherein the refrigeration apparatus is determined based on an internal temperature and a detection result of the frost detection means.   When the inside humidity detecting means for detecting the inside humidity is provided, and the detected value of the inside humidity detecting means is larger than a predetermined value, the inside temperature detecting means and the inside humidity detecting means (Tdp-ET) / (Ta-ET) expressed in advance using the detected internal temperature Ta and internal dew point temperature Tdp, and the evaporation temperature ET detected from the evaporation temperature detecting means. The evaporation temperature ET is determined so as to be smaller than that, and the rotation speed of the compressor is adjusted by the compressor rotation speed adjusting means so as to be the determined evaporation temperature ET. The refrigeration apparatus according to any one of the above.   Until the detection result of the frosting detection means reaches a predetermined value, the rotation speed of the compressor is controlled so as to maintain an evaporation temperature at which the compressor is not thermo-off. The refrigeration apparatus according to any one of claims 1 to 4.   The refrigeration apparatus according to any one of claims 1 to 5, wherein a defrosting start determination of the defrosting operation is performed based on a comparison between a detection result of the frosting detection unit and a predetermined value. .   The refrigeration apparatus according to any one of claims 1 to 6, wherein the frost detection means is arranged on a side where the amount of frost formation increases compared to the windward side and leeward side of the evaporator.   The refrigeration apparatus according to any one of claims 1 to 7, wherein an inlet of the refrigerant is arranged on a side where the amount of frost formation is increased by comparing the windward side and the leeward side of the evaporator.   The refrigerating apparatus according to any one of claims 1 to 8, wherein the frost detection means is movable to detect a frost formation state on the entire surface of the evaporator.   Evaporator outlet temperature detection means for detecting the outlet temperature of the evaporator is provided, the refrigerant superheat degree determined from the evaporation temperature detection means and the evaporator outlet temperature detection means can be controlled by the expansion means, and the load is 10. The target refrigerant superheat degree is decreased in an operation where priority is given to high capacity, and the target refrigerant superheat degree is increased in an operation where priority is given to efficiency with a small load. The refrigeration apparatus described in 1.   The refrigeration according to any one of claims 1 to 10, wherein when the compressor is thermo-on after thermo-off, the rotational speed increase speed of the compressor is made slower than during normal startup. apparatus.

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