ES2932056T3 - Reversible air conditioning unit that performs intelligent defrost operations - Google Patents

Abstract

Reversible air conditioning unit (1) comprising a refrigerant circuit (2) where an external coil (5) is designed to be placed in an outdoor environment and is designed to establish a heat exchange with the air of the outdoor environment (8) ; The refrigeration circuit also comprises an internal coil (9) placed in a casing (10) with a first air inlet (11a) designed to communicate with an indoor environment (6) and configured to suck air from the indoor environment (6) and a first air outlet (12a) designed to communicate with the indoor environment (6) and configured to respectively provide cold or hot air to the indoor environment (6) if the reversible air conditioning unit is operating in summer mode or winter mode; the air conditioning unit (1) providing, during winter mode, a defrost operation in which the refrigerant circuit (2) is reversed to heat the outdoor coil (5) and remove ice that forms on the outdoor coil (5). The casing (20) is provided with a second air inlet (11b) configured to communicate with the external environment (8) and a second air outlet configured to communicate with the external environment (8); Shutter means (13) are provided to the first inlet (11a) and to the first outlet (12a) and to the second inlet (11b) and to the second outlet (12b) and are controlled by an electronic unit (14) which is configured, during forced defrost operations, (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Reversible air conditioning unit that performs intelligent defrost operations

CROSS REFERENCE WITH RELATED REQUESTS

This patent application claims the priority of Italian patent application No. 102019000023745 filed on 12/12/2019.

TECHNICAL FIELD

The present invention relates to a reversible air conditioning unit for performing intelligent defrost operations.

BACKGROUND OF THE INVENTION

As is known, air conditioning units are reversible machines, which can operate in summer mode to cool an indoor environment and can also operate in winter mode to heat such an indoor environment.

When an air conditioning unit operates in winter mode, the compressed gas is forced to expand in the outdoor coil and is compressed in the indoor coil which is heated. A fan is used to direct air into the indoor coil to produce a stream of hot air, which is used to heat the indoor environment. For that reason, the outer coil gets quite cold and a layer of ice can form on the surfaces of the outer coil. As is known, ice acts as a thermal insulator and prevents thermal exchange with air from the outside environment; therefore, the outdoor coil must be defrosted periodically to allow the air conditioning unit to function properly.

For defrost operations, the refrigerant circuit is reversed by changing the position of the reversing valve and for some time the gas is compressed in the outer coil which heats up and melts the ice and vice versa the gas is forced to expand in the inner coil which cools down as it does during normal summer mode. For that reason, during the defrosting operation, a rather cool airflow is provided to the indoor environment.

Accordingly, the defrosting operation involves cooling the indoor environment in an undesired manner; people in the indoor environment may feel discomfort from such an unwanted change in temperature. In addition, the cold air, which is blown into the indoor environment through the vents, might disturb people, if the cold air hits people's heads directly.

The object of the present invention is to provide a reversible air conditioning unit, which solves the above technical problem, operating in an intelligent way.

Document EP 3,093,572 shows a reversible air conditioning unit according to the preamble of claim 1. Other relevant documents are CN 109520072 and CN 110260493.

SUMMARY OF THE INVENTION

The above problem is solved by the present invention, as far as an air conditioning unit is concerned, as defined in claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in accordance with the drawings that represent a preferred non-limiting element of the invention, in which:

Figure 1 shows - in a schematic and simplified way - a reversible air conditioning unit made according to the present invention.

Figure 2 shows the reversible air conditioning unit of Figure 1, working in a first operating position.

Figure 3 shows the reversible air conditioning unit of Figure 1, working in a second operating position; Y

Figure 4 is a flowchart detailing the operations of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In figures 1, 2 and 3, number 1 indicates, as a whole, a reversible air conditioning unit, comprising a refrigerant circuit 2 (of a known type and shown schematically) provided with a compressor 3 (a pair of compressors ) of a known type shown schematically, designed to compress a refrigerant gas.

The air conditioning unit has an outdoor coil 5 which is conveniently placed in an outdoor environment 8, more specifically the outdoor environment of a building B (a wall is shown schematically) enclosing an outdoor environment 6 (eg a room), whose temperature must be controlled. In this way, the outdoor coil 5 is configured to be placed outside the room 6 and is designed to establish a heat exchange with the air of the outdoor environment 8 to provide heat energy or to receive heat energy.

The air conditioning unit 1 has an internal coil 9 that is placed in a casing 10 (shown schematically) provided with a first air inlet 11a that communicates with the indoor environment 6 (for example, by means of a duct C1) and configured to suck air (see the black arrow) from the indoor environment 6 and a first air outlet 12a configured to provide (for example, by means of a duct C2) hot or cold air to the indoor environment 6 (see the arrow).

The container 10 is provided with a second air inlet 11b configured to communicate with the external environment 8 and a second air outlet 12b configured to communicate with the external environment 8.

A shutter device 13 is provided for the first and second inlets 11a, 12a and for the first and second outlets 11b, 12b and is movable between an open position and a closed position under the control of an electronic unit 14, as will be explained below. continuation.

An electric fan 15 is placed in the casing 10 (conveniently, but not necessarily, placed in the center of the elongated casing 10) and is designed to move air from the inlets 11a/11b to the outlets 12a/12b.

An air filter 16 (of known type) is contained in the casing 10 and is positioned to be interposed between the first and second air inlets 11a/11b and the electric fan 15.

The refrigerant circuit 2 also comprises a reversing valve 20, which is connected to the compressor 3, the external coil 5 and the internal coil 9 according to the known scheme using the conduit 21 and is designed to be placed in two operating positions. , namely:

• a first operating position, where the reversible air conditioning unit 1 works in a summer mode and the compressed gas is forced to expand in the inner coil 9 and is compressed in the outer coil 5 - a flow of cooled air is supplied to the indoor environment 6; Y

• a second operating position, where the reversible air conditioning unit 1 works in a winter mode and the compressed gas is compressed in the inner coil 9 and is forced to expand in the outer coil 5 - a flow of warm air is supplied to the indoor environment 6.

The electronic control unit 14, when the air conditioning unit 1 operates in the summer mode indicated above, sends commands to the shutter devices 13, so that the first air inlet 11a is open and the first air outlet 12a is open. it is also open (see figure 2); the second air inlet 11b and the second air outlet 12b are kept closed. In this way, hot air is drawn from the air inlet 11a from the indoor environment 6 and supplied to the internal coil 9, which reduces the air temperature: then cooled air is blown by the drive of the electric fan 15 to the outlet of air 12a and is returned to the interior environment 6, which is refrigerated.

The electronic control unit 14, when the air conditioning unit 1 operates in the winter mode indicated above, sends commands to the shutter devices 13, so that the first air inlet 11a is open and the first air outlet 12a is open. it is also open (figure 2); the second air inlet 11b and the second air outlet 12b are kept closed. In this way, air is sucked from the air inlet 11a from the indoor environment 6 and supplied to the internal coil 9, which increases the temperature of the air: then hot air is blown by the impulse of the electric fan 15 to the outlet of air 12a and is returned to the interior environment 6, which is heated.

The operation of the reversible air conditioning unit 1 in the winter mode contributes to the formation of a layer of ice on the outdoor coil 5; when the electronic control unit 14 detects that the coil must be defrosted (this part will be dealt with in detail by means of figure 4), perform the following operations (if forced defrosting operations are performed, these operations will be dealt with in more detail below):

• activates the closing of the first input 11a (see figure 3) and of the first output 12a by closing the relative plugging devices 23;

• activates the opening of the second input 11b and of the second output 12b by opening the relative plugging devices 13; Y

• sucks in outside air into the container 10 through the second inlet 11b and exhausts the air from the container 10 through the second outlet 12b (see the dashed white arrow) - during the above operation, the temperature of the room increases outer coil 5 (details will be given below) and the ice melting process begins when the refrigerant circuit 2 is reversed.

Accordingly, the casing 10 is kept separated by the ambient air 6 and the cold air flow, which is discharged by the casing 10, is sent to the outdoor environment 8 and thus cannot disturb the people in the environment. interior and/or reduce the temperature of the interior environment 6 in an undesired manner. this is an intelligent operation, since the defrosting operation does not cause any discomfort to people in the indoor environment.

When the defrost operation is finished, the winter mode positions are recovered and the refrigerant circuit 2 is reversed again. If free defrost operations are performed, the first input 11a and the first output 12a can be kept open, as is shown in figure 2, and the second input 11b and the second output 12b do not necessarily have to be open. In this case, even if air is supplied to the room 6, the air temperature is not lowered and discomfort is not felt. Also this part will be discussed in more detail with respect to figure 4.

Referring to Figure 4, electronic unit 14 receives a number of measured parameters (block 100), including:

• measurement of relative humidity UR% of air in the external environment 8;

• Text temperature of air of the external environment 8;

• the pev value of the evaporation pressure; Y

• the elapsed time i_nodefrost, since the last defrost operation.

On the basis of the previously measured parameters, and knowing the type of exchange surface of the external coil 5, the electronic unit 14 calculates (block 105) the estimate of the mm_frost value of a mass of ice that should have formed on the surfaces of outdoor coil 5 after the last defrost operation. This operation can be performed using a formula or using a table containing experimental parameters.

Block 105 is followed by block 110 which checks if the calculated value mm_frost is above a limit value mm_frost-max; in the negative block (mm_frost < mm_frost_max) block 110 returns to block 100 and in the affirmative block (mm_frost > = mm_frost_max) block 110 returns to block 120, which allows defrost operations. The value of mm_frost_max has been determined with experimental tests.

Block 120 is followed by two blocks 130 and 140 that perform parallel operations.

Block 130 calculates i_fd, that is, the time required to perform a defrost operation without reversal of the refrigerant circuit 2 from winter mode to summer mode and with compressor 3 stopped.

Conveniently, i_fd is calculated on the basis of:

• the estimate of the mm_frost value of an ice mass;

• Text temperature of air of the external environment 8; Y

• relative humidity UR% of air of the external environment.

Block 140 calculates a general time limit i_lim for the defrost operation, based on a number of parameters, namely:

• temperature T room of the internal environment 6;

• the compressor load percentage %CMP;

• the coefficient of thermal dispersion; Y

• internal loads.

Blocks 130 and 140 are followed by block 150, which compares T_fd with T_lim and if the calculated time T_fd is less than the i_lim limit, the electronic unit 14 is designed to perform free defrost operations (see block 170).

Accordingly, the electronic control unit 14 performs the following free defrost operations:

• the first input 11a and the first output 12a are kept open (see figure 2);

• the second input 11b and the second output 12b are kept closed (see figure 2);

• disconnection of compressor 3 and adjustment of the fan that works to recirculate air;

• An axial fan 30 coupled with the outer coil 5 is driven at maximum speed.

Accordingly, air is sucked in from the inner space 6 and forwarded to the inner space 6, that is, it is recirculated using the fan 15. During the above operation, the ice on the outer coil 5 melts due to the coolant temperature which is above 0°C -(normally it is between 3 / 4°C. The above operation continues for the time i_fd as set by a clock 155 and when the time i_fd has elapsed, a total mode is resumed winter (block 180) Block 180 is followed by block 100.

If block 150 verifies that i_fd is greater than i_lim, block 150 is followed by a block 160 that calculates i_crd, that is, the time required to perform a defrost operation by reversing refrigerant circuit 2 from winter mode to winter mode. summer mode and with compressor 3 running.

Conveniently, i_crd is calculated based on the estimate of the value of an ice mass mm_frost.

Accordingly, the electronic control unit 14 performs the following forced defrost operations (block 190):

• the fan 30 is completely stopped; activates the closure of the first input 11a and the first output 12a by closing the relative plugging devices 13 (figure 3);

• activates the opening of the second input 11b and of the second output 12b by opening the relative plugging devices 13 (figure 3);

• keeps the compressor 3 running and changes the position of the reversing valve 20;

• sucks in outside air into the container 10 through the second inlet 11b and exhausts the air from the container 10 through the second inlet 12b - during the above operation, the temperature of the outside coil 5 increases as it is compressed the gas in the outer coil and the ice melting process begins.

• the fan 15 runs at full speed.

The above operation continues for the time i_crd as set by a clock 156 and when the time i_crd has elapsed, a full winter mode is resumed (block 180). Block 180 is followed by block 100.

Claims (5)

1. Reversible air conditioning unit (1), comprising: a refrigerant circuit (2), wherein an outdoor coil (5) is designed to be placed in an outdoor environment, and is designed to establish a heat exchange with the air of the outdoor environment (8); The refrigerant circuit also comprises an indoor coil (9) placed in a casing (10) with a first air inlet (11a) designed to communicate with an indoor environment (6) and configured to suck air from the indoor environment (6). and a first air outlet (12a) designed to communicate with the indoor environment (6) and configured to provide, respectively, cold or hot air to the indoor environment (6), if the reversible air conditioning unit is operating in summer mode. or in winter mode, providing the air conditioning unit (1), during winter mode, a defrost operation, where the refrigerant circuit (2) is reversed to heat the outdoor coil (5) and remove ice that forms on the coil outside (5), wherein the casing (10) is provided with a second air inlet (11b) configured to communicate with the external environment (8) and a second air outlet configured to communicate with the external environment (8); sealing means (13) being provided for the first entrance (11a) and for the first exit (12a) and for the second entrance (11b) and for the second exit (12b) and being controlled by an electronic unit (14), which is configured, during forced defrost operations, in which said refrigerant circuit is reversed, to close said first inlet (11a) and said first outlet (12a) and to open said second inlet (11b) and said second outlet ( 12b) to provide an air flow towards the external environment, thus preventing the air flow coming from the casing from being provided to the internal environment (6), characterized because The electronic unit (14) comprises first calculation means (130) designed to calculate the time i_fd necessary to perform a free defrost operation without reversing the refrigerant circuit (2) from winter mode to summer mode and without stopping the compressor; and second comparison means, which checks if i_fd is less than -rjim to perform a free-thaw operation; said air conditioning unit (1) is configured to execute a free defrost operation, in the event that the result of said second comparison means (140) is positive. Air conditioning unit as defined in claim 1, wherein the electronic unit (14) comprises estimation means (100, 105) for calculating the estimate of the mm_frost value of a mass of ice, which would have formed on the surfaces of the outer coil (5) after the last defrosting operation; the electronic unit (14) further comprises comparison means (110) for comparing the estimate of the mm_frost value with a limit threshold mm_frost_max; said comparison means (110) allowing said defrost operation, if the estimate of the mm_frost value is greater than said limit threshold mm_frost_max. Air conditioning unit as defined in claim 2, wherein said estimation means (100, 105) are designed to calculate said value of an ice mass mm_frost based on a number of parameters, including one or more of the following: measurement of relative humidity UR% of air of the external environment (8); the Text temperature of air of the external environment (8); the pev value of the evaporation pressure; Y the elapsed time i_nodefrost, since the last defrost operation. 4. Air conditioning unit as defined in claim 1, wherein the electronic unit (14) is designed to perform the following free defrost operations: • keeps the first input (11a) and the first output (12a) open: • keeps the second entrance (11b) and the second exit (12b) closed; • drives a fan (30) coupled with the external coil (5) to work at its maximum speed; and • disconnects the compressor (3). 5. Air conditioning unit as defined in claim 4, wherein the electronic unit is designed to perform the following defrosting operations: • activates the closing of the first input (11a) and of the first output (12a) by closing the relative plugging devices (13); • activates the opening of the second entrance (11b) and the second exit (12b) by opening the shutter devices (13); • keeps the compressor (3) running and changes the position of the reversing valve (20); controls a fan (15) placed in a casing (10) to operate at maximum speed; draws in outside air into the container (10) through the second inlet (11b) and exhausts air from the container (10) through the second inlet (12b); During the above operation, the temperature of the outer coil (5) increases as the gas in the outer coil is compressed and the ice melting process starts.