CN116608643A - Condensing pressure control method and system for energy conservation of refrigerating device - Google Patents

Abstract

The invention discloses a condensing pressure control method and a condensing pressure control system for energy conservation of a refrigerating device, which specifically comprise the following steps: calculating to obtain the minimum condensing pressure P of the refrigerating device of the refrigerator under the condition of meeting the refrigerating capacity requirement _min The method comprises the steps of carrying out a first treatment on the surface of the The actually detected condensing pressure P of the refrigerating device is compared with the minimum condensing pressure P _min Comparing; according to the condensation pressure P and the minimum condensation pressure P _min Regulating the flow of cooling water to make the condensing pressure P and the minimum condensing pressure P of the refrigerating device _min Equal. The condensing pressure control method provided by the invention can work at lower condensing pressure while ensuring enough refrigerating capacity of the refrigerating device, reduce the load of the compressor, prolong the service life of the compressor and save the energy consumption of the whole refrigerating device.

Description

Condensation pressure control method and system for energy saving of refrigeration device

technical field

The invention relates to the technical field of refrigeration, in particular to a condensation pressure control method and system for energy saving of a refrigeration device.

Background technique

When the condensing pressure of the refrigeration device is reduced to a certain extent, the refrigeration capacity will be reduced accordingly, making it difficult to maintain the cold storage in the set temperature range, especially for the ship refrigeration system, due to the large span of the ship sailing area, seawater is used as cooling When the medium is used, the condensation pressure of the refrigeration device will be greatly reduced, resulting in insufficient cooling capacity and an increase in the temperature of the cold storage. In order to avoid insufficient cooling capacity, the staff need to manually reduce the flow of cooling water to maintain sufficient condensing pressure when necessary, but the specific amount of adjustment requires the staff to have rich experience to complete. In order to facilitate operation, most of the current marine refrigeration equipment directly keeps the condensing pressure constant at a high value to ensure sufficient refrigeration capacity of the refrigeration device. Higher working pressure increases unnecessary energy consumption and is not conducive to equipment life.

Contents of the invention

The invention provides a condensing pressure control method and system for saving energy in a refrigeration device, so as to overcome the problem that the refrigeration compressor is always at a relatively high working pressure and wastes energy due to the inability to accurately judge the actual cooling capacity demand.

In order to achieve the above object, technical scheme of the present invention is:

A condensing pressure control method for energy saving of a refrigeration device, the specific steps are as follows:

Step 1. Calculate and obtain the minimum condensing pressure P _min of the refrigeration device under the condition that the cold storage meets the refrigeration capacity requirements, P _min = [C ₁ (tt ₁ )+C ₂ ] ² +C ₃ , the unit is Pa;

In the formula: t is the ambient temperature, the unit is ℃; t ₁ is the set working temperature of the cold storage, the unit is ℃; C ₁ is a constant determined by the thermal insulation performance of the cold storage and the unit cooling capacity of the refrigeration device, and C ₂ is the change of the cold storage inventory The constant determined by the cooling capacity and the unit cooling capacity of the refrigeration device, _C3 is a constant determined by the refrigerant and the temperature of the cold storage;

Step 2. Comparing the actually detected condensing pressure P of the refrigeration device with the minimum condensing pressure P _min ;

Step 3. Adjust the cooling water flow according to the comparison result of the condensation pressure P and the minimum condensation pressure P _min in step 2, so that the condensation pressure P of the refrigeration device is equal to the minimum condensation pressure P _min .

Further, in the step 1, the values of _C1 and _C2 are as follows:

C ₂ =m·q ₂ /(K ₂ ρ ^0.5 ·q ₁ ),

C ₃ is the evaporation pressure of the refrigerant in the low-temperature storage, and the unit is Pa; where: is the average value of the mass of each newly added item in the cold storage within 12 hours, and the unit is kg/s; c is the specific heat capacity of the newly added item in the cold storage; K ₁ is the average heat transfer coefficient of the cold storage, and the unit is W/°C m ² ; A is the external area of the cold storage, the unit is m ² ; K ₂ is the throttling coefficient of the expansion valve in the refrigeration system; ρ is the density of the refrigerant in the liquid state in the refrigeration system, the unit is kg/m ³ ; q ₁ is Unit cooling capacity, the unit is kJ/kg; q ₂ is the freezing heat of the items added to the cold storage, the unit is kJ/kg.

Further, it includes a control module, a condensation pressure detection module, a temperature detection module, an evaporation pressure detection module, a human-computer interaction module and a cooling water flow adjustment module, and the control module is compatible with the condensation pressure detection module, the temperature detection module, and the evaporation pressure detection module , The human-computer interaction module is electrically connected to the cooling water flow adjustment module;

The condensation pressure detection module transmits the collected condensation pressure signal P to the control module, the temperature detection module transmits the collected ambient temperature signal t to the control module, and the evaporation pressure detection module collects the collected evaporation pressure The signal C ₃ is transmitted to the control module, and the human-computer interaction module transmits the collected m, c, t ₁ , ρ, A, K ₁ , K ₂ , q ₁ , q ₂ signals to the control module;

The control module issues corresponding control commands to the cooling water flow regulating module according to the collected signals, and the cooling water flow regulating module receives the commands and executes corresponding operations.

Further, the control module calculates C ₁ and C ₂ , and further calculates P _min .

Further, P _min =[C ₁ (tt ₁ )+C ₂ ] ² +C ₃ , the unit is Pa.

Further, the control module compares the collected condensation pressure signal P with P _min to obtain comparison results of P<P _min , P=P _min and P>P _min .

Further, when P<P _min or P>P _min , the control module sends an instruction to adjust the cooling water flow regulating valve to the cooling water flow regulating module; when P=P _min , the control module sends an instruction to the cooling water flow regulating valve The regulating module issues an instruction to keep the opening of the cooling water flow regulating valve constant.

Beneficial effects: the present invention analyzes heat balance, that is, the cooling capacity of the device is equal to the heat load of the cold storage at a certain ambient temperature, and the cooling capacity of the device is proportional to the square root of the difference between the condensation pressure and the evaporation pressure, and the thermal load of the cold storage is proportional to the ambient temperature It is directly proportional to the difference between the set temperature _of the cold storage, and the minimum condensing pressure P _min required by the cold storage is obtained through formulating. While meeting the refrigeration capacity requirements, it can work at a lower condensing pressure, reduce the load on the compressor, prolong the life of the compressor, and save the energy consumption of the entire device.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained according to these drawings without any creative effort.

Fig. 1 is the flow chart of steps of the condensing pressure control method among the present invention;

Fig. 2 is a structural block diagram of the condensing pressure control system in the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

This embodiment provides a condensation pressure control method for energy saving of refrigeration equipment, as shown in Figure 1, the specific steps are as follows:

Step 1. Calculate the minimum condensing pressure P _min of the refrigeration device when the cold storage meets the refrigeration capacity requirements. The calculation method for the minimum condensing pressure P _min is:

P _min = [C ₁ (tt ₁ )+C ₂ ] ² +C ₃ (1),

In the formula: t is the ambient temperature, the unit is ℃; t ₁ is the set working temperature of the cold storage, the unit is ℃; C ₁ is a constant determined by the thermal insulation performance of the cold storage and the unit cooling capacity of the refrigeration device, and C ₂ is the change of the cold storage inventory The constant determined by the cooling capacity and the unit cooling capacity of the refrigeration device, _C3 is a constant determined by the refrigerant and the temperature of the cold storage;

Further, considering that the external display of the cold storage may be in different environments in the actual environment, the detected temperature t can also be corrected according to the actual situation in practical applications. Specifically, when different parts of the cold storage are in different temperature environments, The number of ambient temperature sensors can be increased to measure the temperature of different environments respectively; taking the cold storage in 3 different ambient temperatures of a, b, and c as an example, three temperature sensors can be set to respectively measure the corresponding ambient temperatures t _a , t _b , t _c , at this time, the calculation method of formula (1) becomes:

P _min = [C ₁ (tt ₁ )+C _1a (t _a -t ₁ )+C _1b (t _b -t ₁ )+C _1c (t _c -t ₁ )+C ₂ ] ² +C3;

Among them, the constant C ₁ and other calculation methods are:

C _1a =K _1a ·A _a /(K ₂ ρ ^0.5 ·q ₁ );

C _1b =K _1b ·A _b /(K ₂ ρ ^0.5 ·q ₁ );

C _1c =K _1c ·A _c /(K ₂ ρ ^0.5 ·q ₁ );

In the above formulas, A _a , A _b , and A _c are the areas of the cold storage in different temperature environments, and K _1a , K _1b , and K _1C are the corresponding heat transfer coefficients in turn;

Specifically, in the step 1, the values of _C1 and _C2 are as follows:

C ₁ =(m·c+K ₁ ·A)/(K ₂ ρ ^0.5 ·q ₁ ) (2),

C ₂ =m·q ₂ /(K ₂ ρ ^0.5 ·q ₁ ) (3),

_C3 is the evaporation pressure of the refrigerant in the low-temperature storage, and the unit is Pa. In this embodiment, the temperature of the low-temperature storage is -20°C;

In the formula: is the average value of the mass of each newly added item in the cold storage within 12 hours, and the unit is kg/s; c is the specific heat capacity of the newly added item in the cold storage; K ₁ is the average heat transfer coefficient of the cold storage, and the unit is W/°C m ² ; A is the external area of the cold storage, the unit is m ² ; K ₂ is the throttling coefficient of the expansion valve in the refrigeration system; ρ is the density of the refrigerant in the liquid state in the refrigeration system, the unit is kg/m ³ ; q ₁ is Unit cooling capacity, the unit is kJ/kg; q ₂ is the freezing heat of the items added to the cold storage, the unit is kJ/kg.

Specifically, the newly added items will reach the set temperature of the cold storage within 12 hours. Based on the consideration of the cooling speed of the newly added items, m=M÷3600÷12, and M is the average quality of each newly added item;

The calculation method determined by formula (1), formula (2) and formula (3) is based on the heat balance analysis and the collation of the formula. The specific derivation process is as follows:

Assume that the throttling coefficient is K ₂ when the expansion valve can work normally, the density of the refrigerant in liquid state is ρ, the mass flow rate flowing through the expansion valve is m _R , and the pressures before and after the expansion valve are taken as condensation pressure P and evaporation pressure P ₀ , where the evaporation pressure is the saturation pressure of the refrigerant used in the device at the evaporation temperature (it can also be corrected according to the actual situation, such as considering the heat transfer temperature difference, the pressure drop of the refrigerant flowing in the evaporator, etc.), according to the flow rate The relationship to the differential pressure yields:

m _R ＝(PP ₀ ) ^0.5 ρ ^0.5 K ₂ (4)

Assuming that the cooling capacity of the device is Q and the unit cooling capacity is q ₁ , then:

Q＝m _R ·q ₁ (5)

Substituting Equation (4) into Equation (5), the relationship between cooling capacity and pressure can be obtained:

Q＝q ₁ ·(PP ₀ ) ^0.5 ·ρ ^0.5 ·K ₂ (6)

Wherein P ₀ can be determined by the nature of the refrigerant used by the device and the set temperature of the cold storage, and an appropriate correction value can be used in the actual device. In the present invention, the corrected P ₀ is recorded as C ₃ ;

Assuming that the total heat load of the cold storage at ambient temperature t is Q _t , the total heat load is divided into the heat Q ₁ introduced through the insulation layer and the heat introduced by adding items to the cold storage. The calorific value Q ₂ and the heat Q ₃ generated by the freezing phase transition, according to the newly placed items reach the set temperature of the cold storage after 12 hours, the average quality of each new item in the cold storage within 12 hours is recorded as m, and the new cold storage The specific heat capacity of the added item is denoted as c, the average heat transfer coefficient of the cold storage is denoted as K ₁ , the external area of the cold storage is denoted as A, and the freezing heat of the item added to the cold storage per unit mass is denoted as q ₂ , then:

Q _t =Q ₁ +Q ₂ +Q ₃ (7)

Q ₁ =K ₁ ·A·(tt ₁ ) (8)

Q2＝m·c·(tt ₁ ) (9)

Q3＝m·q ₂ ·(tt ₁ ) (10)

Substituting Equation (8), Equation (9), and Equation (10) into Equation (7), the total heat load of the cold storage can be obtained.

In order to make the cooling capacity of the device not less than the heat load of the cold storage, the Q determined by formula (6) should not be less than the _Qt determined by formula (7), that is:

Q _min = Q _t (11)

In the above formula, Q _min is the minimum value of Q that meets the requirements, solve the equations about the condensation pressure P determined by formula (6) to formula (10), and record the condensation pressure corresponding to Q _min as P _min , which can be The relational expressions described in the foregoing formula (1), formula (2), and formula (3) are obtained.

Step 2. Comparing the actually detected condensing pressure P of the refrigeration device with the minimum condensing pressure P _min ;

Step 3. Adjust the cooling water flow according to the comparison result of the condensation pressure P and the minimum condensation pressure P _min in step 2, so that the condensation pressure P of the refrigeration device is equal to the minimum condensation pressure P _min .

Specifically, according to the comparison result of P and P _min , the cooling water flow rate is adjusted as follows:

When P<P _min , reduce the cooling water flow to make P=P _min ;

When P>P _min , increase the cooling water flow to make P=P _min .

Based on the same inventive concept, the present invention also provides a condensing pressure control system for energy saving of refrigeration devices, as shown in Figure 2, including a control module, a condensing pressure detection module, a temperature detection module, an evaporation pressure detection module, a man-machine An interaction module and a cooling water flow adjustment module, the control module is electrically connected to a condensation pressure detection module, a temperature detection module, an evaporation pressure detection module, a human-computer interaction module and a cooling water flow adjustment module;

The condensation pressure detection module transmits the collected condensation pressure signal P to the control module, the temperature detection module transmits the collected ambient temperature signal t to the control module, and the evaporation pressure detection module collects the collected evaporation pressure The signal C ₃ is transmitted to the control module, and the human-computer interaction module transmits the collected m, c, t ₁ , ρ, A, K ₁ , K ₂ , q ₁ , q ₂ signals to the control module;

The control module issues corresponding control commands to the cooling water flow regulating module according to the collected signals, and the cooling water flow regulating module receives the commands and executes corresponding operations.

In this embodiment, the condensation pressure detection module is a pressure sensor, the temperature detection module is a temperature sensor, and the evaporation pressure detection module is an evaporation pressure sensor; the cooling water flow regulating valve can be a throttle valve or a three-way valve according to the specific pipeline conditions.

The control module calculates C ₁ and C ₂ , and further calculates P _min , wherein P _min =[C ₁ (tt ₁ )+C ₂ ] ² +C ₃ , and the unit is Pa.

The control module calculates C 1 and C ₂ according to m, c, ρ, A, K ₁ , K ₂ , q ₁ , q _{2 ,} and then calculates P according to C ₁ , C ₂ , C ₃ , t and t _{1 min} .

In the present invention, the calculated _C1 and _C2 can also be manually input to the human-computer interaction module, and the collected _C1 and _C2 signals are transmitted to the control module by the human-computer interaction module, and the control module is based on C ₁ , C ₂ , C ₃ , t and t ₁ calculate P _min .

The control module compares the collected condensation pressure signal P with P _min to obtain comparison results of P<P _min , P=P _min and P>P _min .

When P<P _min or P>P _min , the control module sends an instruction to adjust the cooling water flow regulating valve to the cooling water flow regulating module; when P=P _min is equal, the control module sends an instruction to the cooling water flow regulating module Issue an instruction to keep the opening of the cooling water flow regulating valve constant.

Specifically, if P<P _min , the control module outputs a mediation signal to close the cooling water flow regulating valve until the condensing pressure detected by the pressure sensor is P=P _min , the output signal is 0, and the cooling water flow regulating valve remains open No change; if P>P _min , the control module outputs a mediation signal to open the cooling water flow regulating valve until the output signal is 0 when the condensing pressure detected by the pressure sensor is P=P _min , and the opening of the cooling water flow regulating valve remains unchanged ; If the opening of the cooling water flow regulating valve reaches the maximum and P is still greater than P _min , then the cooling water flow regulating valve maintains the maximum opening.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (7)

1. The condensing pressure control method for the energy conservation of the refrigerating device is characterized by comprising the following specific steps:

step 1, calculating to obtain the minimum condensing pressure P of the refrigerating device of the refrigerator under the condition that the refrigerating capacity requirement is met _min ，P _min ＝[C ₁ (t-t ₁ )+C ₂ ] ² +C ₃ Pa is taken as a unit;

wherein: t is the ambient temperature, and the unit is taken; t is t ₁ The unit is taken as the set working temperature of the refrigeration house; c (C) ₁ C is a constant determined by the heat preservation performance of the refrigeration house and the unit refrigerating capacity of the refrigeration device ₂ C is a constant determined by the stock change of the refrigeration house and the unit refrigerating capacity of the refrigerating device ₃ Is a constant determined by the temperature of the refrigerant and the refrigeration house;

step 2, the actually detected condensing pressure P of the refrigerating device is compared with the minimum condensing pressure P _min Comparing;

step 3, condensing pressure P and minimum condensing pressure P according to the step 2 _min Regulating the flow of cooling water to make the condensing pressure P and the minimum condensing pressure P of the refrigerating device _min Equal.

2. The condensing pressure control method for energy saving of refrigerating apparatus according to claim 1, wherein in said step 1, C ₁ And C ₂ The values of (2) are as follows: c (C) ₁ ＝(m·c+K ₁ ·A)/(K ₂ ρ ^0.5 ·q ₁ )，

C ₂ ＝m·q ₂ /(K ₂ ρ ^0.5 ·q ₁ )，.

C ₃ Taking Pa as the evaporation pressure of the refrigerant in the low-temperature reservoir; wherein: m is an average value of the mass of the newly added articles in the refrigeration house in 12 hours, and the unit is kg/s; c is the specific heat capacity of the newly added article in the refrigeration house; k (K) ₁ The unit is W/DEG C.m for the average heat transfer coefficient of the refrigeration house ² The method comprises the steps of carrying out a first treatment on the surface of the A is the outer surface area of the refrigeration house, and the unit is m ² ；K ₂ Is the throttling coefficient of an expansion valve in the refrigeration system; ρ is the density of the refrigerant in the refrigeration system in kg/m ³ ；q ₁ The unit is the refrigerating capacity, and kJ/kg is taken in unit; q ₂ To obtain the freezing heat of the article to be added into the refrigerator, kJ/kg is taken in units.

3. The condensing pressure control system for energy conservation of the refrigerating device is characterized by comprising a control module, a condensing pressure detection module, a temperature detection module, an evaporating pressure detection module, a man-machine interaction module and a cooling water flow regulating module, wherein the control module is electrically connected with the condensing pressure detection module, the temperature detection module, the evaporating pressure detection module, the man-machine interaction module and the cooling water flow regulating module;

the condensing pressure detection module transmits the collected condensing pressure signal P to the control module, the temperature detection module transmits the collected ambient temperature signal t to the control module, and the evaporating pressure detection module transmits the collected evaporating pressure signal C ₃ Transmitting the acquired m, c and t to the control module, wherein the man-machine interaction module acquires the acquired m, c and t ₁ 、ρ、A、K ₁ 、K ₂ 、q ₁ 、q ₂ Transmitting signals to the control module;

the control module issues corresponding control commands to the cooling water flow regulating module according to the acquired signals, and the cooling water flow regulating module receives the commands and executes corresponding operations.

4. A condensing pressure control system for chiller energy conservation according to claim 3 wherein the control module calculates C ₁ And C ₂ Further calculate P _min 。

5. The condensing pressure control system for chiller energy savings of claim 4, wherein P _min ＝[C ₁ (t-t ₁ )+C ₂ ] ² +C ₃ The unit is Pa.

6. The condensing pressure control system for chiller energy conservation of claim 4, wherein the control module is configured to collect the condensing pressure signals P and P _min Comparing to obtain P < P _min 、P＝P _min P > P _min Is a comparison result of (a).

7. The condensing pressure control system for chiller energy savings according to claim 6 wherein when P < P _min Or P > P _min When the cooling water flow regulating valve is in a closed state, the control module sends a command for regulating the cooling water flow regulating valve to the cooling water flow regulating module; when p=p _min And when the opening degree of the cooling water flow regulating valve is unchanged, the control module sends an instruction for keeping the opening degree of the cooling water flow regulating valve unchanged to the cooling water flow regulating module.