KR20200111067A - Condensing pressure control method of heat pump - Google Patents

Abstract

The present invention relates to a heat pump control method and, more specifically, to a heat pump control method including a compressor, a condenser, a liquid refrigerant storage space, an expansion valve, an evaporator, and a condenser fan. The heat pump control method controls the amount of compression per unit time of the compressor according to the size of the indoor heat load, wherein a target condensation temperature (Tc_t) of the condenser is a value obtained by adding a predetermined value (c1, hereinafter ″offset″) to the outside air temperature (Ta), the offset (c1) is the temperature difference between a condensation temperature (Tc) and the outside air temperature (Ta), which is the optimum efficiency at the minimum design load, when the condensation temperature (Tc) is higher than the target condensation temperature (Tc_t), the speed of the condenser fan is increased (than present), and when the condensation temperature is lower, the speed of the condenser fan is further lowered (than present) to achieve the target condensation temperature, when the outside temperature increases from a lower side to a higher side, the (excess) liquid refrigerant stored in the liquid refrigerant storage space decreases.

Description

Condensing pressure control method of heat pump}

The present invention relates to a method of controlling the condensing pressure (temperature) of a heat pump.

A heat pump is a device that transfers heat from a heat source to a destination called a “heater sink”. Heat pumps absorb heat in cold spaces and dissipate heat in warm spaces. That is, in the heat pump, heat energy is transferred in a direction opposite to the natural heat transfer direction. To this end, the heat pump uses a small amount of external energy to transfer energy from the heat source to the heat sink.

Air conditioners, refrigerators and air conditioners (HVAC: Heating Ventialating and Air Conditioning) are representative examples of heat pumps. In addition, devices using a heat pump include water purifiers, dryers, washing machines, and vending machines that provide cold/hot water.

In the ISO 15042:2017 hip pump performance test and evaluation standard, there are several test conditions, such as overload test conditions, standard test conditions, and low load test conditions. The amount of charged refrigerant at which the system efficiency is optimal has different problems for each of the above test conditions.

In order to optimize the system efficiency, methods of controlling the condensation temperature (pressure) in US2018073791 A1, US20160131405 A1, etc. have been suggested. However, the procedures are complicated. In addition, since the control method of each component is not clearly presented, it is difficult to implement it in practice.

According to the data sheet of commercially available condenser fan speed controllers, the input of the speed controller is high pressure (condensing pressure), and the fan speed is controlled by a value (linearly proportional to the input value) (see Fig. 1). And as a result of fan speed control, the amount of condensation is changed to stabilize the high pressure (condensation pressure). That is, if the condensation pressure increases due to various variables, there is a problem of performing passive control so that the condensation pressure is increased slightly, and when the condensation pressure is lowered, it is slightly lowered.

US20180073791 A1 US20160131405 A1

Johnson Controls (May 2018), “P266 Series Single-Phase Condenser Fan Speed Controls”, Code No. LIT-12011534, p3 Danfoss, (April 2018), ”Fan speed controller type Saginomiya RGE”, DKRCC.PD.LA0.C1.02, p2

The present invention is derived to solve the problems of the prior art. More specifically, it is to provide a heat pump that intuitively and easily adjusts the condensation temperature in order to optimize system efficiency.

A heat pump control method of the present invention relates to a heat pump control method including a compressor, a condenser, a liquid refrigerant storage space, an expansion valve, an evaporator, and a condenser fan, and more particularly, the unit of the compressor according to the size of the indoor heat load. The amount of compression per hour is adjusted, and the target condensation temperature (Tc_t) of the condenser is a value obtained by adding a predetermined value (c1, hereinafter “offset”) to the outside air temperature (Ta); Wherein, the offset (c1) is a temperature difference between the condensation temperature (Tc) and the outside temperature (Ta), which is the optimum efficiency at the minimum design load; If the condensation temperature (Tc) is higher than the target condensation temperature (Tc_t), the speed of the condenser fan is increased (than current), and if it is lower, the speed of the condenser fan is lowered (than present) to achieve the target condensation temperature. And, when the outside temperature increases from a lower side to a higher side, the (excess) liquid refrigerant stored in the liquid refrigerant storage space decreases; It features.

At this time, the condenser fan uses the value of the load at which saturation starts and the offset (c1) value at the maximum load, and obtains a target condensation temperature of the load between the two load values by interpolation; This is desirable.

In addition, when the speed of the condenser fan is saturated, the opening degree larger than the current opening degree (eg, 110% opening degree of the current opening degree) and the opening degree smaller than the current opening degree (eg, 90% opening degree of the current opening degree) are selected [predetermined time. At intervals (eg, 15 seconds)] to achieve the target condensation temperature by repeatedly controlling it alternately; This is desirable.

In addition, the interval between the minimum load and the maximum load is divided into a number of load sections, the offset (c1) of each load section increases as it goes from the minimum load to the maximum load, and the speed of the condenser fan in each load section tends to increase. And, at the end of each load section, the speed of the condenser fan (FN_C) is the maximum design speed, and the difference between the offset value (c1) from the adjacent load section is 5 °C or less; This is desirable.

In addition, the offset (c1) is 5 to 12 ℃; This is desirable.

A heat pump control method according to the present invention includes a heat pump including a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, comprising: an outdoor refrigerant storage space installed between the outdoor heat exchanger and the expansion valve; An indoor refrigerant storage space installed between the indoor heat exchanger and the expansion valve; And a four-way side for switching the connection of the compressor. And, when the heat pump operates in the cooling mode, the liquid refrigerant is stored in the outdoor refrigerant storage space, the indoor refrigerant storage space serves as a pipe, and when the heat pump operates in the heating mode, it is stored in the indoor refrigerant storage space. Storing a liquid refrigerant, and the outdoor refrigerant storage space serving as a pipe; This is desirable.

A heat pump control method according to the present invention is a heat pump including a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger, comprising: a first four-way side for switching the connection of the compressor; A second four-way side for switching the connection of the expansion valve; And a liquid refrigerant storage space installed between the expansion valve and the second four sides. This is desirable.

According to the heat pump control method of the present invention, there is an effect of providing a heat pump with improved system efficiency by actively controlling the condensation temperature during operation of the heat pump.

1 shows a method for controlling a condenser fan speed according to the prior art.
2 is a circuit diagram of a heat pump according to the present invention.
3 is basic data for explaining the present invention.
Figure 4 shows the preferred target condensation temperature in the present invention.
5 shows an optimal amount of refrigerant charged and stored in the present invention.
Figure 6 is a preferred condenser fan speed control method in the present invention.
7 is another preferred condenser fan speed control method in the present invention.
8 is a ph diagram for explaining the effect of the present invention.
9 is another preferred heat pump circuit diagram in the present invention.
10 is another preferred heat pump circuit diagram according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this case, it should be noted that in the accompanying drawings, the same components are indicated by the same reference numerals as possible. Spatially relative terms "below", "beneath", "lower", "above", "upper", etc., as shown in the figure It can be used to easily describe the correlation between components and other components. In addition, in the present specification, the term "pressure" may be interpreted as "a temperature at which the refrigerant boils, condensation temperature, or evaporation temperature".

The terms used in the present specification are for describing exemplary embodiments and are not intended to limit the present invention. In this specification, the singular form also includes the plural form unless specifically stated in the phrase. As used in the specification, "comprises" and/or "comprising" refers to the presence or addition of one or more other components, steps and/or actions. Do not exclude

In addition, terms or words used in the present specification and claims described below should not be interpreted as being limited to a conventional or dictionary meaning, but should be interpreted as meanings and concepts consistent with the technical idea of the present invention. In addition, detailed descriptions of known configurations and functions that are determined to unnecessarily obscure the subject matter of the present invention will be omitted.

In the following description, for convenience, an ideal heat pump will be used unless otherwise specified.

An object of the present invention is to control the condensation temperature by storing excess refrigerant in a refrigerant storage space, and as a result, to provide a heat pump with high efficiency.

<Explanation of core concepts>

The heat exchange amount of the air heat exchanger can be calculated as Q = c·m·dT. Here, there are many combinations of m and dT that make Q equal. In the above formula, m can be interpreted as air volume, air weight, wind speed, heat exchanger fan speed, fan power consumption, etc. (though it may vary depending on air humidity). Here, c is the air specific heat or proportionality coefficient. And the temperature difference dT (=air temperature before passing through the heat exchanger-air temperature after passing through) can be changed by the temperature difference between the temperature at which the refrigerant boils inside the heat exchanger and the incoming air. For convenience of explanation, in the present specification, m is described using “the fan speed”.

In more detail, if the heat exchanger temperature (in other words, the temperature at which the refrigerant boils in the heat exchanger) and the air temperature are the same, no heat exchange occurs. One of the methods of reducing the temperature difference dT is to reduce the difference between the temperature of the air flowing into the heat exchanger and the boiling temperature of the refrigerant inside the heat exchanger. When the pressure inside the heat exchanger is changed, the temperature at which the refrigerant boils in the heat exchanger is controlled, and it is natural that this is related to the power consumption of the compressor.

In general, if the power consumption of components with relatively low power consumption is increased, the power consumption of components with high power consumption is lowered, and heat exchange is performed according to the heat load, it is natural that the efficiency of the heat pump is improved. For example, in the case of a passenger car air conditioner, the electric compressor capacity is about 3.5 kW, and the heat exchanger fan is about 150 W (approximately 5% of the compressor). In most cases, if the power consumption of the fan is maximized, the power consumption of the compressor is lowered, and heat exchange is performed according to the heat load, the efficiency of the heat pump will be improved compared to the prior art.

In the present invention, per unit time 1) the amount of refrigerant compressed by the compressor, 2) the amount of refrigerant condensed in the condenser, 3) the amount of refrigerant passing through the expansion valve, and 4) the amount of refrigerant evaporated in the evaporator; It is based on controlling to be like this.

In addition, under normal operating conditions, the excess refrigerant overcharged is made into a liquid state, and the high pressure is controlled to be lower than when the excess refrigerant is in a gaseous state.

<Main parts control method>

Hereinafter, a method for controlling (preferred cooling mode) of the main parts of the heat pump will be described with reference to FIG. 2.

In Figure 2, the heat pump 100 is a compressor (C), a condenser (HX_C), a liquid refrigerant storage space (RS), an expansion valve (EXV) and an evaporator (HX_E) are connected in the above-described order to form a refrigerant circulation circuit. Achieve. In addition, it is preferable that the heat pump 100 further includes a sensor PT for measuring temperature and pressure and a condenser fan FN_C at the outlet of the condenser HX_C.

1) Determine the size of the indoor load: Ld_in=(Tm_indoor-Ts_indoor) x indoor space size

The indoor load Ld_in may be determined by a difference between the measured value Tm_indoor of the indoor temperature and the set value Ts_indoor of the indoor temperature. When the heat pump is physically installed, a number of experiments are performed, and the size of the indoor load (Ld_in) can be expressed in %. In this specification, unless otherwise stated, the indoor load (Ld_in) will be described as being in units of %. And, the maximum (design) indoor load that the heat pump can provide is 100%.

2) Variable displacement compressor drive

The compressor is driven to achieve the target refrigerant amount per unit time (Refrigerant Amount by Compressor, hereinafter “RAcp”) according to the size of the indoor load (Ld_in). (In the following, it should be noted that “per unit time” is omitted unless specifically emphasized, and is simply expressed as “refrigerant compressed amount”.)

One of the variable performance compressors, an inverter compressor, achieves a target refrigerant compression amount per unit time (hereinafter "RAcp_t") by changing a compressor driving frequency. For example, if the indoor load (Ld_in) is 100%, 100 gram/sec refrigerant is compressed in the compressor (at this time, if RAcp_t is expressed as %, it is 100%, that is, for the maximum design indoor load). Refrigerant compression amount per unit time is 100%), and when the indoor load (Ld_in) is 20%, the compressor drive frequency is controlled to compress the refrigerant 20 gram/sec (at this time, when RAcp_t is expressed as %, it is 20%).

Actually, the amount of refrigerant compression per unit time (RAcp) varies depending on the refrigerant density, refrigerant temperature and compressor temperature at low pressure when the drive frequency of the inverter is fixed. However, the above factors have a smaller influence than the driving frequency. Therefore, in the present specification, the “compressor driving frequency change” may be a simple driving frequency change, or may be a change in consideration of the above various factors. This is because cost and quality are considered when actually implementing a heat pump. More specifically, a heat pump that prioritizes cost will simply adopt a method of changing the driving frequency, and a heat pump that prioritizes quality will adopt a method of changing the driving frequency in consideration of the above factors. .

In the present invention, in the normal operating condition of the heat pump, it is preferable to change the compressor driving frequency according to the size of the indoor load Ld_in. That is, it should be noted that the compressor drive frequency is not controlled to make the discharge pressure of the compressor a predetermined value.

3) Measurement of subcooling

The degree of subcooling (hereinafter, “SC”) is an index indicating how low the condensed liquid refrigerant is below the condensing temperature, and is preferably obtained by the formula below.

Tpcm = f (Pcm)

SC = Tcm-Tpcm

Here, Pcm is the measurement pressure and Tcm is the measurement temperature. These values were measured with a sensor (PT) that measures the temperature and pressure. In addition, Tpcm, which is the theoretical condensing temperature, is the theoretical boiling temperature of the refrigerant at the measured pressure Pcm.

In addition, there are many more conventional techniques for obtaining a preferred subcooling degree in the present invention, but a detailed description thereof will be omitted.

4) Expansion valve (EXV) and evaporator control

In the present invention, since the expansion valve EXV is not particularly limited, all types of expansion valves can be used. In other words, both an electronic expansion valve (hereinafter, "EEV") and a mechanical expansion valve (TXV, capillary tube...) can be used.

4-1) When using a mechanical expansion valve

In the case of using a mechanical expansion valve, since it operates mechanically, there is no need to control the expansion valve by a controller (eg, microcomputer, small computer, etc.) capable of calculation. At this time, the speed of the evaporator fan FN_E is preferably controlled according to the size of the indoor load Ld_in. Since there are a number of prior art for this, a detailed description will be omitted.

4-2) In case of controlling superheat degree with electronic expansion valve

Since there are a number of prior art for controlling the superheat degree with an EEV, a detailed description will be omitted.

At this time, the speed of the evaporator fan FN_E is preferably controlled in proportion to the size of the indoor load Ld_in. Since there are a number of prior art for this, a detailed description will be omitted.

4-3) When controlling the refrigerant passage per unit time with an electronic expansion valve

One preferred control method of an EEV in the present invention is the opening of the EEV so that a refrigerant amount flowing through expansion valve (RAvv) per unit time and a target compression amount (RAcp_t) of the compressor are the same. Is to control. (In the following, it should be noted that “per unit time” is omitted unless specifically emphasized, and is simply expressed as “refrigerant passing amount”.)

To this end, it is possible to measure the refrigerant passage amount (RAvv) for each EEV opening degree (under a number of high and low pressure conditions) as a previous experiment, and make this as a table, or make a formula for calculating the refrigerant passage amount (RAvv) for each EEV opening degree. Is of course.

Then, calculate the heat exchange amount when all the refrigerants that have passed through the EEV are vaporized for each EEV opening (under multiple high and low pressure conditions), and make a heat exchange amount table [corresponding to the indoor load (Ld_in)] for each EEV opening. Or, it is natural that a formula to obtain the heat exchange amount for each EEV opening degree can be made.

At this time, it is preferable to control the superheat (SH) at the speed of the evaporator fan (FN_E). More specifically, basically, when the indoor load (Ld_in) increases than the present, the speed of the evaporator fan (FN_E) also increases. In addition, the speed of the evaporator fan FN_E may increase or decrease in the indoor load Ld_in having an arbitrary value, in order to control the superheat SC to a predetermined value.

As mentioned in the background art, there is no single optimal refrigerant charge for multiple test conditions. One of the ways to solve this is to control the amount of gas refrigerant in the high pressure section.

For example, in a heat pump using a thermal expansion valve (TXV), the amount of refrigerant in the low pressure section will be almost constant under a specific load. And, the rest of the charged refrigerants are all present in the high-pressure part. When a certain amount of refrigerant coexists as gas and liquid in the high-pressure part, the pressure changes according to the amount of gas. That is, if you want to lower the high pressure more than the present, the high-pressure gas refrigerant becomes a liquid refrigerant, so that the gas refrigerant is less than the present. In the present invention, the liquid refrigerant is stored in the refrigerant storage space RS. For reference, the refrigerant storage space RS may be inside the condenser HX_C.

Hereinafter, a method of controlling the condensation temperature (cooling mode) preferred in the present invention will be described with reference to FIGS. 3 to 7.

3 is an example conceptually showing the condenser fan speed 31 according to the size of the load. That is, as the load size increases, the condenser fan speed 31 also increases. [At this time, the test conditions, outdoor temperature (Ta) and condensation temperature (Tc) are constant values. ]

In the case of a general home, when the outside temperature increases, the indoor load tends to increase as well. Therefore, when the outside temperature increases, the condenser fan speed 37 also tends to increase. In the case of a restaurant kitchen that uses a lot of fire, the interior load may be high even when the outside temperature is within the design lower limit. In other words, the indoor load may always be high regardless of the outside temperature. In addition, when a predetermined period of time has elapsed since the heat pump is operated and the indoor temperature reaches near the set temperature, the load decreases. Then, the indoor load can always be low regardless of the outside temperature.

Regardless of the outside temperature, it has been described above that the indoor load can be a value between the design minimum value and the design maximum value. The preferred condensation temperature in the present invention is preferably formed as high as a predetermined value (c1, hereinafter “offset”) to the outside temperature as shown in (41) of FIG. 4. If this is expressed in the formula, the target condensation temperature (Tc_t) = outside temperature (Ta) + offset (c1).

FIG. 5 conceptually shows the refrigerant charge amount 51 required to form the optimum condensation temperature for each outdoor temperature. When the outside temperature rises, the refrigerant charge amount 51 must also increase to achieve the optimum condensation temperature. The optimum refrigerant charge amount 51 is the sum 51 of the amount of refrigerant required to form a low pressure, the amount of gaseous refrigerant required to form a high pressure, and the amount of liquid refrigerant 53 stored in the condenser HX_C.

It is preferable to make the excess refrigerant 57 overcharged under normal operating conditions into a liquid and store it in the refrigerant storage space RS. At this time, it is natural that the excess refrigerant 57 increases as the outside temperature decreases.

Hereinafter, a preferred condensation temperature control method in the present invention will be described with reference to FIG. 6.

The condensing temperature (o_tc) and the condenser fan speed (o_fspd) according to the prior art tend to increase as the load increases. (Figure 1 is expressed differently)

In the present invention, the difference between the condensation temperature (Tc), which is the optimum efficiency, and the outside temperature at the minimum design load, is set as an offset (c1), and is applied to an equation for obtaining the target condensation temperature (Tc_t). Then, the target condensation temperature Tc_t has a constant value (if the outside temperature does not change) in the entire load range. 6 shows an example in which the target condensation temperature Tc_t is 50°C.

In Fig. 6, when the load increases from 20% to 68%, the condensation temperature (o_tc) also increases in the prior art. However, the condensation temperature according to the present invention is fixed to the target condensation temperature Tc_t obtained at the minimum design load. Therefore, the amount of heat exchange due to the difference between the target condensation temperature Tc_t and the outside air temperature Ta becomes smaller than that of the prior art except for the minimum design load. In order to compensate for this, it is preferable to operate the condenser fan (FN_C) faster to supply more air used for heat exchange to the condenser (HX_C) (eg, fspd_2). (Q=c.m.dT=constant, dT keeps a small value, m value is a high value)

Therefore, when the condenser fan (FN_C) is driven below the design maximum speed (=100% speed), it is preferable to control the condensation temperature (Tc) to the target condensation temperature (Tc_t) at the speed of the condenser fan (FN_C). Do. At this time, it is natural that the condensation temperature Tc may be the theoretical condensation temperature of the refrigerant or the condensation temperature measured by the condenser EX_C.

When the condenser fan FN_C is driven below the design maximum speed, the (theory) condensation temperature is determined by the amount of gas refrigerant present at high pressure. Therefore, in the present invention, when the high pressure is high (i.e., the current condensation temperature is higher than the target value), the speed of the fan is increased to condense the gas refrigerant more than the present, and the high pressure (condensation temperature) is lowered to achieve the above goal. desirable. On the contrary, if the high pressure is low (that is, if the current condensation temperature is lower than the target value), it is desirable to achieve the above goal by increasing the high pressure (condensation temperature) by lowering the fan speed to condense the gas refrigerant less than the current one. . Then, the excess refrigerant is converted into a liquid refrigerant at a certain outside air temperature and automatically stored in the storage space RS.

In Fig. 6, when the load was increased from 68% to 100%, the condenser fan FN_C was saturated at the design maximum speed. Therefore, the target condensation temperature Tc_t cannot be maintained, and the condensation temperature Tc rises along the curve Tc_2, and finally becomes the same as the conventional condensation temperature Tc.

Here, the condensation temperature inflection point (eg, 68% in FIG. 6) moves toward the load 100% when the heat exchange amount margin of the actual product is large, and moves toward the minimum design load value when the margin is small. (It occurs a lot when improving the existing products that are already installed)

If the speed (fspd_2) of the condenser fan (FN_C) is not saturated and can continue to rise (e.g., up to 150% of the prior art), the target condensation temperature (Tc_t) can be achieved in the entire load range. Of course. This is desirable in cases where there are no restrictions on the installation space of the condenser and fan.

On the other hand, when the speed of the condenser fan (FN_C) is saturated (e.g., in the 68% to 100% load section in Fig. 6), there is a problem that it is not possible to actively control the condensation temperature (Tc_2) to an appropriate value. . More specifically, if there is an excess gas refrigerant, it cannot be converted into a liquid refrigerant. 7 is a condenser fan (FN_C) speed control method to solve this problem. If the condenser fan (FN_C) speed rises from below the saturation value to the saturation value, increase the temperature offset by a predetermined value (eg, c1_a to c1_b, or c1_b to c1_c). In other words, if the condensation temperature is increased, dT increases at Q=c.m.dT, so the amount of heat exchange matches the load by lowering m by the fan (FN_C). (As a number of previous experiments, it is desirable to store the load value at which the condensation temperature changes, the change in the condensation temperature (delta Tc), and the fan (FN_C) speed in a table.)

When the load goes down from the maximum design load value to the minimum design load value, it is natural that the fan (FN_C) speed can be controlled based on the previously obtained table. At this time, it is preferable to add hysteresis characteristics to the point at which the condensation temperature is changed.

As described above, since the speed of the condenser fan FN_C is not saturated in the entire load region, the excess refrigerant can be stored in the liquid refrigerant storage space RS.

In FIG. 7, the target condensation temperature Tc_t was constant in three load sections. In more detail, the offset (c1) is (c1_a), (c1_b) and (c1_c) in the 20% ~ 68% section, 68% ~ 85% section, and 85% ~ 100% section of the load, respectively, and the target condensation temperature (Tc_t) was achieved. (Formula: Tc_t = Ta + c1) And at this time, the speed of the fan (FN_C) in each section is (fspd_a) (fspd_b) and (fspd_c). It is preferable that the speed of the condenser fan (FN_C) at the end of each load section is the maximum design speed. And it is preferable that the offset (c1) of each load section increases as it goes from the minimum load to the maximum load. And it is preferable that the difference between the offset value (c1) from the adjacent load section is 5 °C or less. This is because the smaller the offset value with the adjacent load section, the higher the efficiency and the more complicated the control.

Hereinafter, when the load increases from 68% to 100% in FIG. 6 (that is, when the speed of the condenser fan is saturated to the maximum design value), another method of storing the excess refrigerant will be described.

In the present invention, each component is controlled so that the amount of refrigerant compressed by the compressor (C), the amount of refrigerant condensed by the condenser (HX_C), the amount of refrigerant passing through the expansion valve (EXV), and the amount of refrigerant evaporated from the evaporator (HX_E) are the same per unit time. . Therefore, if the condensed high-pressure refrigerant is not sent down to a low pressure, the condensed refrigerant will be stored in the refrigerant storage space RS. In other words, the amount of condensed refrigerant is constant, but the liquid refrigerant increases because the condensed refrigerant is not sent down to a low pressure. As a result, the excess refrigerant is stored in the storage space RS and the condensation temperature is lowered.

As a specific value, for example, if the current condenser fan (FN_C) speed is 100% and the current expansion valve opening is 70% of the design maximum opening, at the 70% expansion valve opening, the amount of refrigerant corresponding to the load passes through the expansion valve. Is done. However, when the expansion valve opening is lowered to a level of 80% of the current opening (that is, 56% = 70% x 80%), a smaller amount of refrigerant is supplied to the evaporator HX_E than that required by the load. In this case, some of the condensed liquid refrigerant is stored in the storage space RS, so that the condensation temperature is lowered. For reference, it is preferable to repeatedly control the expansion valve opening by alternating the opening corresponding to 100% of the current load and the opening corresponding to 80% of the current load [at a predetermined time interval (eg, 15 seconds)].

In addition, if the condenser fan's speed is saturated, the opening is larger than the current opening (eg, 110% of the current opening) and the opening is smaller than the current opening (eg, 90% of the current opening). (Eg, 15 seconds)] It is desirable to achieve the target condensation temperature by repeatedly controlling it alternately. At this time, since the target condensation temperature becomes (Tc_2), it is desirable to check the offset value for each load size in advance as a previous experiment. Also, if you know the load value at which the condenser fan starts saturation and the offset at the maximum load, the target condensation temperature of the load between the two load values is (linear) interpolated to obtain the target condensation temperature (Tc_2). I can.

In the formula Tc_t = Ta + c1 for obtaining the target condensation temperature, the offset (c1) is preferably 5 ~ 12 ℃. If the offset (c1) is too low at the lowest design load, the required amount of heat exchange may not be performed. Therefore, considering the subcooling degree (SC) 2 ~ 5 ℃ and the extra temperature 3 ~ 7 ℃, the offset (c1) is 5 ~ 12 ℃. This is because the optimum subcooling degree and extra temperature can change depending on how the actual system is implemented.

According to a number of documents, in a heat pump using an inverter compressor, the condensation temperature at the maximum load and the condensation temperature at the minimum load differ from about 8°C to 10°C. Assuming that the condensation temperature difference due to the inverter compressor conservatively differs by 8°C, the efficiency of the cooling cycle is calculated with specific values. First, cycles 91-(92)-(93-(94), which are widely used in automobile air conditioner design (refer to Fig. 8), have a condensing temperature/evaporation temperature of 60 ℃ / 0 ℃. Assuming that the temperature is 5 ℃, the equivalent enthalpy efficiency of the compressor is 70%, and the heat loss of the compressor is 10%, the COP is 2.254. And, according to the present invention, the condensation temperature is not increased (ie, it is designed to suppress the rise of 8 ℃). The COP of cycles 91-(72)-(73)-(74) is 2.782, which is 23% more efficient than before the condensation temperature was suppressed.

9 is another configuration of a heat pump preferred in the present invention. The heat pump 200 is a liquid refrigerant outdoor storage space (RSE) installed between the four sides (4WC) for switching the connection of the compressor (C) to the heat pump 100, the outdoor heat exchanger (HX_EX) and the expansion valve (EXV) And a liquid refrigerant indoor storage space (RSI) installed between the indoor heat exchanger (HX_IN) and the expansion valve (EXV) was added. The outdoor storage space RSE stores a liquid refrigerant in a cooling mode, and the indoor storage space RSI stores a liquid refrigerant in a heating mode. Here, it is preferable that air is provided from the outdoor heat exchanger fan FN_EX in the outdoor storage space RSE. In addition, it is preferable that air is supplied from the indoor heat exchanger fan FN_IN in the indoor storage space RSI.

10 is another preferred configuration of a heat pump in the present invention. The heat pump 300 includes a four-way side (4WC) for switching the connection of the compressor (C) to the heat pump 100, a four-way side (4WR) for switching the connection of the expansion valve (EXV), and the expansion valve (EXV). A liquid refrigerant storage space (RS3) installed between the expansion valve switching four sides (4WR) was added.

With the present invention, a heat pump capable of controlling the condensation temperature can be manufactured in various configurations. In addition, it is possible to provide an optimal heat pump in consideration of the purpose (for cooling only, for both cooling and heating), the limitation of installation space, and the price of each component.

It is natural that the liquid refrigerant storage space can be manufactured integrally with the condenser. This is particularly useful for heat pumps that only require cooling (because they can supply heat required for heating) such as internal combustion engine cars and fuel cell cars.

In addition, since excess refrigerant can be stored, it is also desirable to allow the heat pump to operate normally even if a certain amount (eg, half of the initial refrigerant charge) leaks in consideration of a case where the refrigerant leaks.

In the present invention, it is exemplified that the target condensation temperature is one and three, which are obtained by a linear formula in the entire load region. According to the spirit of the present invention, it is natural that the number of target condensation temperatures is not limited to a specific number.

As described above, the preferred embodiments of the present invention have been described, but these are only examples, and those of ordinary skill in the art will understand that various modified embodiments are possible therefrom. Therefore, the embodiments of the present invention disclosed in the present specification and drawings are merely provided for specific examples to easily explain the technical content of the present invention and to aid understanding of the present invention, and are not intended to limit the scope of the present invention.

According to the heat pump control method of the present invention as described above, since it is possible to increase the performance (COP) of the heat pump by preventing the gap between the high pressure and the low pressure from increasing during the operation of the heat pump, industrial use is very high.

In particular, in the case of automobiles, since the fuel economy of the air conditioner operated vehicle is improved and the amount of greenhouse gas (CO2) generated by the air conditioner is reduced, the possibility of industrial use is very high.

C Compressor PT temperature, pressure sensor
HX_C condenser RS refrigerant storage space
HX_E evaporator EXV expansion valve
31 Condenser fan speed per load
37 Load characteristics of ordinary homes
41 Condensation temperature according to the outside air of the present invention
51 Optimum amount of refrigerant according to the outside temperature
53 Amount of liquid refrigerant inside the condenser that achieves optimum efficiency for each outside temperature
57 Amount of stored liquid refrigerant that produces optimum efficiency by ambient temperature
Tc_t target condensation temperature
Tc_2 realized condensing temperature
c1_a c1_b c1_c condensation temperature offset
o_tc Condensation temperature of the prior art
o_fspd Condenser fan speed of the prior art
fspd_2, fspd_a fapd_b fspc_c condenser fan speed
RSE, RSI refrigerant storage space
HX_EX, HX_IN heat exchanger
FN_EX, FN_IN heat exchanger fan
4WC, 4WR all sides

Claims (7)

In the heat pump control method comprising a compressor, a condenser, a liquid refrigerant storage space, an expansion valve, an evaporator and a condenser fan,
Adjusting the compression amount per unit time of the compressor according to the size of the indoor heat load; And,
The target condensation temperature (Tc_t) of the condenser is a value obtained by adding a predetermined value (c1, hereinafter “offset”) to the outside air temperature (Ta); and,
The offset (c1) is a temperature difference between the condensation temperature (Tc) and the outside air temperature (Ta), which is the optimum efficiency at the minimum design load; ego,
If the condensing temperature Tc is higher than the target condensing temperature Tc_t, the speed of the condenser fan is increased (than current), and if it is low, the speed of the condenser fan is lowered (than present) to achieve the target condensing temperature,
When the outside temperature increases from a lower side to a higher side, the (excess) liquid refrigerant stored in the liquid refrigerant storage space decreases; Heat pump control method, characterized in that.
The method of claim 1,
The condenser fan is obtained by interpolating the target condensation temperature of the load between the two load values by using the value of the load at which saturation starts and the offset (c1) value at the maximum load; Heat pump control method, characterized in that.
The method of claim 2,
When the speed of the condenser fan is saturated, the opening degree larger than the current opening degree (eg, 110% opening degree of the current opening degree) and the opening degree smaller than the current opening degree (eg, 90% opening degree of the current opening degree) are selected at [a predetermined time interval ( Eg, 15 seconds)] to achieve the target condensation temperature by alternately controlling it repeatedly; Heat pump control method, characterized in that.
The method of claim 1,
The minimum load to the maximum load is divided into multiple load sections,
The offset (c1) of each load section increases from the minimum load to the maximum load,
The speed of the condenser fan in each load section tends to increase,
The speed of the condenser fan (FN_C) at the end of each load section is the maximum design speed,
The difference between the offset value (c1) and the adjacent load section is 5 ℃ or less; Heat pump control method, characterized in that.
The method of claim 1,
The offset (c1) is 5 to 12 ℃; Heat pump control method, characterized in that.
In a heat pump comprising a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger,
An outdoor refrigerant storage space installed between the outdoor heat exchanger and the expansion valve;
An indoor refrigerant storage space installed between the indoor heat exchanger and the expansion valve; And
Further comprising a four-way side for switching the connection of the compressor; and,
When the heat pump operates in the cooling mode, liquid refrigerant is stored in the outdoor refrigerant storage space, and the indoor refrigerant storage space serves as a pipe,
When the heat pump operates in the heating mode, the liquid refrigerant is stored in the indoor refrigerant storage space, and the outdoor refrigerant storage space serves as a pipe; Heat pump, characterized in that.
In the heat pump comprising a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger,
A first four-way side for switching the connection of the compressor;
A second four-way side for switching the connection of the expansion valve; And
A liquid refrigerant storage space being installed between the expansion valve and the second four sides; Heat pump, characterized in that.

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