JPH08285390A - Freezing device for container - Google Patents

Abstract

PURPOSE: To eliminate a lack of dehumidifying capability while a suitable capability controlling operation is being kept without stopping an operation of a compressor by a method wherein a modulating valve is installed at a bypass circuit connecting an outlet port of the compressor to a midway part of an evaporator coil. CONSTITUTION: During a capability control operation, gaseous refrigerant of high pressure and high temperature at an outlet port of a compressor 1 flows into a midway part of an evaporator coil 51 so as to adjust a cooling capability. Then, the refrigerant adjusted by an electronic expansion valve 4 and adiabatically expanded to become double-layer of gas-liquid state of low pressure and low temperature enters an evaporator 5 as it is, where the refrigerant cools the air fed into the refrigerator and is evaporated and gasified. A proper amount of gaseous refrigerant of high pressure and high temperature at an outlet port of the compressor 1 flows through a modulating valve 8 at the midway part of the evaporator coil 51 and mixed with it. At this time, a connecting position of the bypass circuit 7a is set to be 40% to 70% location from an inlet part of the evaporator coil 51, thereby it is possible to realize both superior capability control function and dehumidifying capability.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a refrigerating unit for a container.

[0002]

2. Description of the Related Art A container stores cargo in its container and operates a refrigerating unit to keep the internal temperature of the container at a set temperature and to load it on ships, trucks, rail cars, etc. for transportation.

A conventional example of this type of refrigerating unit is shown in FIG.

When the refrigeration unit is operated, the gas refrigerant discharged from the compressor 1 enters the condenser 2 where it radiates heat to the outside air sent by the condenser blower 3 to be condensed and liquefied. The liquid refrigerant is adiabatically expanded by being throttled by the electronic expansion valve 4, and then enters the evaporator 5, where the inside air sent by the evaporator blower 6 is cooled to evaporate and return to the compressor 1. . A modulating valve 8 is provided in a bypass circuit 7 that connects the outlet of the compressor 1 and the inlet of the evaporator 5.

The evaporator 5 comprises an evaporator coil 51 formed by bending a pipe into a U-shape in multiple layers and a large number of fins 52 closely attached to the outer circumference of the evaporator coil 51. The evaporator coil 51 is divided into an appropriate number of circuits, and each circuit is connected in parallel with the refrigerant circuit. Further, 10 is a flow divider that divides the refrigerant entering the evaporator coil 51 into each circuit.

Reference numeral 20 denotes a controller for controlling the operation of the refrigeration unit, which is housed in a control box (not shown).

The controller 20 has a temperature control function for maintaining the inside temperature at a set temperature, and when the operating state becomes abnormal,
It has a self-diagnosis function for taking measures such as stopping the refrigeration unit, a display / recording function, etc. Here, only the temperature control function will be described below.

The controller 20 sets the temperature Ts from the inside temperature setting device 21 and the inside temperature Ti from the inside temperature sensor 9 to the controller 20.
Has been entered in. The controller 20 first compares the temperature with a predetermined temperature (for example, −5 ° C.) stored in itself to determine the operation mode. That is, if the set temperature Ts is equal to or higher than the predetermined temperature, the refrigerating mode is set, and if the set temperature Ts is lower than the predetermined temperature, the freezing mode is set.

In the refrigerating mode, the temperature control is determined by the on / off control of the compressor 1, and the temperature deviation Δ in the refrigerator is determined.
T (ΔT = Ts−Ti) is within a predetermined allowable range (eg ± 3
ON / OFF of the compressor 1 is determined so that the compressor 1 enters into the compressor 1, and the determination result of this ON / OFF is input to the compressor 1, and the compressor 1 is driven or stopped.

At this time, the modulating valve 8 is fully closed.

In the refrigerating mode, the compressor 1 is not stopped (continuous operation), and a high-pressure and high-temperature gas refrigerant at the outlet of the compressor 1 is electronically expanded through the bypass circuit 7 and the modulating valve 8 in an appropriate amount. An operation in which the cooling capacity of the refrigeration unit is adjusted to match the load by mixing the refrigerant that has been adiabatically expanded by being throttled by the valve 4 and mixed in a low-pressure low-temperature gas-liquid two-phase state (hereinafter, this operation will be referred to as capacity). Controlled driving). Then, the internal temperature deviation ΔT (Δ
T = Ts-Ti) is within a predetermined allowable range (for example, ± 0.2d).
The degree of opening of the modulating valve 8 is determined so as to be in (eg ° C), and the determined degree of opening is input to the modulating valve 8, and the regulating valve 8 is controlled to the determined degree of opening.

FIG. 4 shows a temperature change due to heat exchange between the refrigerant and the air in the evaporator 5 during the capacity control operation.

In FIG. 4, low pressure and low temperature (for example, EP =
1.47 Kg / cm ² G {0.14 MPa}, ET =-
At a high pressure and high temperature (for example, CP = 22.2 Kg / cm ² {2.
2 MPa}, CT = 55 ° C., DT = 110 ° C.), an appropriate amount of the gas refrigerant is mixed through the modulating valve 8 and flows into the evaporator 5 in this state.

As a result, depending on the cooling load, the liquid state of the refrigerant is completely evaporated (for example, superheat degree SH = 5de).
It flows into the evaporator 5 at g ° C., point A in FIG. 4). Then, SH is further increased by cooling the inside air introduced into the evaporator 5 (for example, SH = 15 ° C., point B in FIG. 4).
It flows out from the evaporator 5. In this case, since the refrigerant does not contain a liquid component at the inlet of the evaporator 5, it has a cooling capacity near the inlet, but the refrigerant temperature is high in most of the downstream of the evaporator 5, and the cooling capacity is low. Almost gone.

[0015]

The conventional container refrigeration unit described above has the following problems to be solved.

That is, in the conventional refrigeration unit, during the capacity control operation, the cooling capacity of the refrigeration unit is adjusted in accordance with the cooling load, so that the modulating valve 8 is opened without stopping the compressor 1. The degree of discharge gas is controlled and an appropriate amount of discharge gas is bypassed to the inlet of the evaporator 5.

Therefore, when the cooling load is small, the bypass amount of the discharge gas is increased, and the refrigerant in the state of superheated vapor containing no liquid flows into the inlet of the evaporator 5.
As shown in FIG. 4, the refrigerant temperature in the evaporator 5 becomes high.
As a result, the surface temperature of the fins 52 of the evaporator 5 also rises and becomes close to the dew point temperature (for example, 0 ° C.) of the inlet air of the evaporator 5.

Therefore, in this case, the moisture in the air does not condense on the surface of the fin 52, and the dehumidifying capacity of the refrigerating unit is almost lost.

This has a problem that it has a high internal humidity and is suitable for cargo such as vegetables and fruits requiring high humidity, but not suitable for cargo such as bulbs requiring low humidity.

An object of the present invention is to provide a refrigerating unit for containers that solves the above problems.

[0021]

As a means for solving the above problems, the present invention is to provide a container refrigerating unit described in (1) and (2) below.

(1). In a container refrigeration unit in which the temperature inside the container in which cargo is stored is maintained at a set temperature by operating the refrigeration unit with capacity control by the hot gas bypass system, connect the outlet of the compressor and the middle of the evaporator coil. A refrigerating unit for a container, comprising a bypass circuit and a modulating valve interposed in the bypass circuit.

(2). In the container refrigeration unit described in (1) above, a bypass circuit is connected to a place within a range of 40 to 70% from the inlet of the evaporator coil.

[0024]

Since the present invention is constructed as described above, it has the following actions.

(1). In the configuration of (1) above, since the bypass circuit connecting the outlet of the compressor and the middle of the evaporator coil and the modulating valve interposed in the circuit are provided, the expansion valve is provided at the evaporator coil inlet. Refrigerant that is in a low-pressure low-temperature gas-liquid two-phase state flows in by being throttled at, and this refrigerant cools the inside air that has been introduced into the evaporator in the process of passing through the evaporator coil,
It evaporates and vaporizes itself. Then, in the middle of the evaporator coil, the evaporated and vaporized low-temperature refrigerant is heated from the outlet of the compressor to a high-pressure, high-temperature gas refrigerant through a bypass circuit and a modulating valve to be heated to a high temperature. . The hot gas refrigerant heats the cooled inside air in the process of passing through the evaporator coil. By the above cooling and heating, it exerts a cooling capacity as a whole corresponding to the cooling load, has the same function as the conventional one, and the refrigerant temperature upstream of the place where the bypass circuit is connected is low in the middle of the evaporator coil. Therefore, the temperature of the evaporator (fin) surface in this part can be made sufficiently lower than the dew point temperature of the evaporator inlet air,
It is possible to dehumidify the inside air while cooling it.

(2). In the configuration of (2) above, since the bypass circuit of the configuration of (1) above is connected to a portion within a range of 40 to 70% from the inlet of the evaporator coil, the function of capacity control operation is appropriately performed. The dehumidifying ability is also properly exerted.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. The same components as those in FIG. 3 of the conventional example are designated by the same reference numerals, and the description thereof will be omitted unless necessary.

FIG. 1 is a schematic configuration diagram of a container refrigerating unit according to the present embodiment, and FIG. 2 is a diagram showing changes in the modes of air and refrigerant in an evaporator according to the present embodiment.

In FIG. 1, reference numeral 7a denotes a bypass circuit connecting the outlet of the compressor 1 and the middle of the evaporator coil 51, and 8
Is a modulating valve installed in the bypass circuit 7a. Other configurations and operations are similar to those of the conventional example shown in FIG. 3, and corresponding members are designated by the same reference numerals.

Next, the operation of the above configuration will be described.

In the capacity control operation, the high-pressure and high-temperature gas refrigerant at the outlet of the compressor 1 flows into the evaporator coil 51, and the cooling capacity is adjusted.

The temperature change due to heat exchange between the refrigerant and the air in the evaporator 5 in this embodiment will be described with reference to FIG. (For example, EP = 1.47 Kg / cm ²
The refrigerant in a gas-liquid two-phase state of G {0.14 MPa}, ET = -20 ° C) enters the evaporator 5 as it is, and evaporates and evaporates by cooling the inside air introduced therein. Then, in the middle of the evaporator coil 51, the high pressure and high temperature (for example, C
P = 22.2 Kg / cm ² G {2.2 MPa}, (T =
A gas refrigerant of 55 ° C., DT = 110 ° C.) flows in and mixes through the modulating valve 8 in an appropriate amount, so that the refrigerant temperature rises (for example, 30 ° C., FIG. 2A).
Point) As a result, the air cooled upstream of the evaporator 5 is heated downstream and exhibits a cooling capacity equivalent to that of the conventional one as a whole.

The refrigerant temperature upstream of the evaporator 5 is low (for example,-
20 ° C.), the surface temperature of the fins 52 is sufficiently lower than the dew point temperature of the inlet air of the evaporator 5 (for example, 0 ° C.). Therefore,
Moisture in the air is condensed on the surfaces of the fins 52 to dehumidify the air in the refrigerator, so that the humidity in the refrigerator can be maintained at a low level.

In the above description, the evaporator coil 51
It was confirmed by experiments that the connection position of the bypass circuit 7a in the middle of the step was set to 40% to 70% from the inlet of the evaporator coil 51 so that good performance control function and dehumidification performance could be exhibited.

As described above, according to the present embodiment, the refrigerant temperature is low upstream of the position where the bypass circuit 7a of the evaporator coil 51 is connected, so that the air entering the evaporator 5 is sufficiently cooled to below the dew point temperature. Dehumidify and bypass circuit 7a
In the downstream of the position where is connected, a suitable amount of high-temperature and high-pressure gas refrigerant discharged from the compressor 1 is mixed, so the inside air cooled as described above is appropriately warmed, and the cooling capacity as a whole matches the cooling load. There is an advantage that can be exhibited.

Further, as described above, the inside air is appropriately dehumidified, so that there is an advantage that it is suitable for storing bulbs and the like which require low humidity.

[0037]

The present invention has the following effects because it is configured as described above.

That is, in the present invention, since the refrigerant temperature is maintained at a low temperature in the upstream portion of the portion where the bypass circuit is connected in the middle of the evaporator coil, the evaporator (fin) surface temperature in this portion is set to the evaporator inlet. The temperature can be made sufficiently lower than the dew point temperature of air, and the air inside the refrigerator introduced into the evaporator can be cooled and simultaneously dehumidified.

Then, the inside air cooled by the evaporator is heated by the evaporator downstream of the bypass circuit connection point, and by this cooling and heating, the cooling capacity corresponding to the cooling load can be exerted as a whole. .

Since dehumidification is possible during cooling in this way, it is possible to maintain low humidity inside the refrigerator, and it can be applied to cargo such as bulbs that require low humidity.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention,

FIG. 2 is a diagram showing a mode change of air and refrigerant in the evaporator according to the above embodiment,

FIG. 3 is a schematic configuration diagram of a conventional refrigeration unit,

FIG. 4 is a diagram showing changes in the states of air and refrigerant in an evaporator of a conventional refrigeration unit.

[Explanation of symbols]

 1 Compressor 5 Evaporator 7a Bypass circuit 8 Modulating valve 51 Evaporator coil

Claims (2)

[Claims] 1. An outlet of a compressor and an evaporator coil in a container refrigeration unit in which the temperature inside a container for storing cargo is maintained at a set temperature by performing capacity control operation of the refrigeration unit by a hot gas bypass system. A refrigeration unit for containers, comprising: a bypass circuit connecting the middle of the refrigeration circuit and a modulating valve interposed in the bypass circuit. 2. The refrigeration unit for containers according to claim 1, wherein the bypass circuit is connected to a portion within a range of 40 to 70% from the inlet of the evaporator coil.