CN105091398B - A kind of refrigerating output control methods of New Type of LiBr Absorption Chiller group - Google Patents

Abstract

The invention discloses a novel lithium bromide absorption refrigerating unit, comprising a generator, a condenser, an evaporator, an absorber, a solar heat collector cycle heating system, a solution heat exchanger, a PLC control system, and a touch screen connected to the PLC control system display, the solar heat collector cycle heating system includes a solar heat collector connected in turn to form a hot water circulation loop through pipelines, a hot water electric control valve, a hot water pump, a generator inlet temperature transmitter, a flow transmitter The generator, the generator outlet temperature transmitter, the hot water electric control valve, the generator inlet temperature transmitter, the flow transmitter, and the generator outlet temperature transmitter are all connected to the PLC control system circuit. The invention also provides a method for adjusting the cooling capacity of a novel lithium bromide absorption refrigeration unit. The invention effectively improves the refrigeration efficiency of the lithium bromide absorption refrigerator driven by the low-temperature heat source, and reduces the minimum driving heat source temperature required by the refrigeration system.

Description

A method for adjusting the cooling capacity of a new lithium bromide absorption refrigeration unit

technical field

The invention relates to the technical field of mechanical manufacturing and control, in particular to a novel lithium bromide absorption refrigeration unit and a cooling capacity adjustment method thereof.

Background technique

The lithium bromide absorption refrigerator has low operating cost, no moving parts, long life, no noise, meets the requirements of energy saving and environmental protection, and has a wide application prospect. However, the current lithium bromide absorption refrigerator has a relatively high temperature requirement for the driving heat source due to the limitation of the technical ability development level, and the current general solar collector can only provide low-quality heat source, which cannot reach the required temperature, and the efficiency is relatively low. Difficult to promote in the market. The core of the unit control system is the energy regulation system. Its main goal is to match the heat load required by the outside world with the cooling capacity of the lithium bromide refrigeration unit at all times, which is reflected in the outlet temperature of the refrigerant water of the unit. Since the heat load required by the outside world exists Fluctuating, so the cooling capacity requirements of the unit also change accordingly. The energy regulation system needs to monitor and adjust the driving heat source and solution circulation volume to economically and stably meet the operating requirements of the system.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a novel lithium bromide absorption refrigerating unit and its cooling capacity adjustment method, in order to effectively improve the refrigerating efficiency of the lithium bromide absorption refrigerating machine driven by a low-temperature heat source, and reduce the refrigeration system. The lowest driving heat source temperature promotes its market promotion.

The novel lithium bromide absorption refrigerating unit provided by the invention is realized through the following technical solutions:

A new type of lithium bromide absorption refrigerating unit, including a generator and a condenser arranged in a high-pressure chamber, an evaporator and an absorber arranged in a low-pressure chamber, a solar collector circulation heating system that provides hot water for the generator, Solution heat exchanger, PLC control system, touch screen display connected to the PLC control system, the evaporator is used to exchange heat with the target refrigerant water, and the solar heat collector circulation heating system includes a hot water circulation loop formed by sequentially connecting pipelines The solar collector, hot water electric control valve, hot water pump, generator inlet temperature transmitter, flow transmitter, generator outlet temperature transmitter, the hot water electric control valve, generator inlet temperature The transmitter, flow transmitter, and generator outlet temperature transmitter are all connected to the PLC control system circuit;

A solution pump is arranged between the solution heat exchanger and the absorber to pump the lithium bromide dilute solution to the generator through the solution heat exchanger, and the solution pump is connected to the PLC control system circuit through a frequency converter;

The target refrigerant water inlet pipe of the evaporator is provided with an evaporator inlet temperature transmitter, and the target refrigerant water outlet pipe of the evaporator is provided with an evaporator outlet temperature transmitter.

Further, it also includes an ultrasonic strengthening device, the transducer of the ultrasonic strengthening device is directly installed at the bottom of the high-pressure chamber, and the ultrasonic strengthening device uses the ultrasonic cavitation effect to strengthen the mass transfer and heat transfer process of the lithium bromide-water solution in the generator;

Further, the frequency of the ultrasonic intensifier is above 20kHz, and the working power is above 100w.

Further, the number of transducers is ≥ 1. When the number exceeds 1, the installation positions between adjacent transducers are equal and not less than 100mm. Specifically, it can be determined according to the scale of the unit and the structure of the high-pressure chamber and its The bottom area can be properly adjusted, and the installation method can be high-strength glue, mechanical installation, and magnetic adsorption.

Further, a closed-loop control system is adopted between the hot water electric control valve and the PLC control system to improve the adjustment accuracy of the hot water electric control valve.

The refrigerating capacity adjustment method of the novel lithium bromide absorption refrigerating unit provided by the present invention is realized by the following scheme:

A method for adjusting the cooling capacity of the novel lithium bromide absorption refrigerating unit, comprising the steps of:

1) The PLC control system compares the actual temperature Tr of the target refrigerant water outlet of the evaporator acquired by the evaporator outlet temperature transmitter in real time with the set temperature Ts set by the touch screen display;

2) If 1°C≤|Tr‐Ts|<5°C, the PLC control system first adopts the circulating fluid frequency conversion speed regulation mode, that is, calls the PID algorithm to adjust the frequency of the frequency converter, so that the frequency converter acts on the solution pump connected to it, and passes through the solution The pump controls the circulating flow rate of the lithium bromide dilute solution of the unit, and then adjusts the cooling capacity until |Tr‐Ts|﹤1℃.

Further, if |Tr‐Ts|≥5℃, further steps:

3) Check the working status of the hot water electric control valve (6) and the inverter, and judge the working status of the unit and the static time of the hot water electric control valve (6), so as to ensure that there will be no excessive adjustment and avoid frequent operation of the hot water electric control valve. regulating valve;

4) If the unit is not in full-load working condition and the hot water electric control valve (6) has been static for 3 minutes, then start the mode of adjusting the hot water supply at the same time, that is, the PLC control system generates a signal, and the signal makes the hot water electricity Control the opening of the control valve (6) to increase or decrease by 5%. By optimizing the cooling capacity adjustment method, that is, the intelligent combination of circulating fluid frequency conversion speed regulation technology and hot water supply adjustment mode is used to comprehensively adjust the target refrigerant water outlet temperature. , improve mediation efficiency and accuracy;

5) After the opening of the hot water electric control valve (6) is in place, stand still for 3 minutes, and then the PLC control system will obtain the temperature of the target refrigerant water outlet of the evaporator (13) obtained in real time by the evaporator outlet temperature transmitter (1). The actual temperature Tr is compared with the set temperature Ts set through the touch screen display, if |Tr‐Ts|<1°C, the cooling capacity adjustment is completed, otherwise, return to step 3).

Furthermore, when the actual temperature Tr is higher than the set temperature Ts, if the inverter frequency and the opening of the hot water electric control valve have reached the upper limit, the unit will maintain the current working state; when the actual temperature Tr is lower than the set temperature Ts , if the frequency of the frequency converter and the opening of the hot water electric control valve have reached the lower limit, the PLC control system will start a yellow alarm signal, and at the same time the unit will stop, stop cooling for dilution, and protect the system from crystallization and other failures.

Further, when the PLC control system generates a signal to control the opening of the hot water electric control valve, the hot water electric control valve will timely feed back the current opening to the PLC control system through the closed-loop control system, and the PLC control system will Judging and ensuring that the hot water electric control valve stops when it reaches the target opening, forming a closed-loop control to improve the adjustment accuracy of the hot water electric control valve.

Compared with the prior art, the present invention has the following beneficial effects:

The new lithium bromide absorption refrigeration unit and its cooling capacity adjustment method proposed by the present invention, in terms of composition and structure, the lithium bromide unit is equipped with an ultrasonic strengthening device on a general basis, and the ultrasonic cavitation effect is used to strengthen the transmission of lithium bromide-water solution in the generator. Mass and heat transfer process; in terms of the cooling capacity adjustment method, by optimizing the cooling capacity adjustment method, the circulating fluid frequency conversion speed regulation technology is intelligently combined with the hot water supply adjustment mode to comprehensively adjust the target refrigerant water outlet temperature. This new type of lithium bromide absorption refrigeration unit can effectively improve the refrigeration efficiency of the lithium bromide absorption refrigeration unit driven by a low-temperature heat source, reduce the minimum driving heat source temperature required by the refrigeration unit, and achieve the goal of cooling capacity adjustment more effectively and economically. Destroy the stable operation characteristics of the system. The adjustment method is applicable to a solar absorption refrigeration system driven by low-temperature hot water, thereby enhancing the cooling effect of the solar air conditioner and promoting its market promotion.

Description of drawings:

Fig. 1 is the structural representation of the novel lithium bromide refrigerating unit of the embodiment of the present invention.

Fig. 2 is a schematic side view of the installation of the transducer of the ultrasonic strengthening device of the novel lithium bromide refrigeration unit according to the embodiment of the present invention.

Fig. 3 is a three-dimensional schematic diagram of the installation of the transducer of the ultrasonic strengthening device of the novel lithium bromide refrigeration unit according to the embodiment of the present invention.

Fig. 4 is an overall scheme diagram of a cooling capacity adjustment method of a novel lithium bromide absorption refrigeration unit according to an embodiment of the present invention.

Fig. 5 is a detailed flowchart of the cooling capacity adjustment method of the novel lithium bromide absorption refrigerating unit according to the embodiment of the present invention.

Reference signs include: 1-evaporator outlet temperature transmitter; 2-evaporator inlet temperature transmitter; 3-ultrasonic strengthening device; 4-generator outlet temperature transmitter; 5-solar collector; 6- Hot water electric control valve; 7‐hot water pump; 8‐generator inlet temperature transmitter; 9‐flow transmitter; 10‐generator; 11‐high pressure cavity; 12‐condenser; 13‐evaporator; 14‐absorber; 15‐low pressure chamber; 16‐solution pump; 17‐solution heat exchanger; 18‐transducer.

detailed description

In order to better understand the present invention, the specific implementation methods of the present invention will be further described below in conjunction with the accompanying drawings and examples, but the protection scope of the present invention is not limited thereto.

Embodiment one

As shown in Figure 1, this embodiment is based on the general structure of a small solar lithium bromide absorption refrigerator with a design cooling capacity of 10KW driven by 85°C hot water, and an ultrasonic strengthening device is added to utilize the ultrasonic cavitation effect , to strengthen the mass transfer and heat transfer process of lithium bromide-aqueous solution in the generator, as follows:

A new lithium bromide absorption refrigerating unit, including a generator 10 and a condenser 12 arranged in a high-pressure chamber 11, an evaporator 13 and an absorber 14 arranged in a low-pressure chamber 15, and a device for providing hot water to the generator 10 Solar heat collector circulation heating system, solution heat exchanger 17, PLC control system, touch screen display connected to the PLC control system, the evaporator 13 is used for heat exchange with target refrigerant water, and the solar heat collector circulation heat supply The system includes a solar collector 5 connected in turn to form a hot water circulation loop through pipelines, a hot water electric control valve 6, a hot water pump 7, a generator inlet temperature transmitter 8, a flow transmitter 9, and a generator outlet temperature transmitter. The transmitter 4, the hot water electric control valve 6, the generator inlet temperature transmitter 8, the flow transmitter 9, and the generator outlet temperature transmitter 4 are all connected to the PLC control system circuit. A closed-loop control system is adopted between the water electric control valve 6 and the PLC control system to improve the adjustment accuracy of the hot water electric control valve;

A solution pump 16 is arranged between the solution heat exchanger 17 and the absorber 14 to pump the lithium bromide dilute solution to the generator 10 through the solution heat exchanger 17, and the solution pump 16 is controlled by a frequency converter and a PLC. circuit connection;

An evaporator inlet temperature transmitter 2 is arranged on the target refrigerant water inlet pipe of the evaporator 13 , and an evaporator outlet temperature transmitter 1 is arranged on the target refrigerant water outlet pipe of the evaporator 13 .

Specifically, this embodiment also includes an ultrasonic strengthening device 3, the transducer 18 of the ultrasonic strengthening device 3 is directly installed at the bottom of the high-pressure chamber 11, and the ultrasonic strengthening device uses the ultrasonic cavitation effect to strengthen the lithium bromide- The mass transfer and heat transfer process of the aqueous solution; the ultrasonic intensification device shown has a generating frequency of 25kHz, a working power of 500w, and 5 transducers 18, which are directly installed at the bottom of the high-pressure chamber where the generator 10 is located, between different transducers 18 The installation position interval is 250mm, and the installation method adopts magnetic adsorption (see eg 2 and Figure 3). The working mode of the ultrasonic strengthening device is to start and stop in random groups, and the unit continues to run during the cooling period.

The refrigerating unit provided in this embodiment utilizes the solar heat collector 5 to convert solar energy into thermal energy to heat water and provide hot water for the generator 10 of the unit. When the lithium bromide refrigerator is working, the working medium absorbs the heat from the hot water and generates refrigerant vapor. The refrigerant vapor flows into the condenser 12, is absorbed by the cooling water, condenses into a liquid, and then enters the low pressure through the throttle valve. The cavity 15 is absorbed and evaporated by the evaporator 13, which takes away the heat of the external refrigerant water to cool it down, and the cooled external refrigerant water enters the indoor unit to generate a cooling effect. The refrigerant water vapor produced by evaporation flows into the absorber 14 and is absorbed by the lithium bromide concentrated solution. After absorbing the refrigerant water vapor, the lithium bromide concentrated solution becomes a lithium bromide dilute solution, and the lithium bromide dilute solution is sent to the generator 10 through the solution pump 16. In this way, the change of the mass fraction of the water-lithium bromide working medium is used to complete the solution circulation and produce cooling capacity. Wherein, in order to improve the thermal efficiency of the unit, a solution heat exchanger 17 is provided for preheating before the lithium bromide dilute solution enters the generator 10 .

The refrigerating unit provided in this embodiment utilizes an ultrasonic intensifier to generate an ultrasonic cavitation effect to strengthen the mass transfer and heat transfer process of the lithium bromide-water solution in the generator 10; and the PLC control system can obtain the actual temperature according to the evaporator outlet temperature transmitter 1 The difference with the set temperature automatically adjusts the opening of the frequency converter and the hot water electric control valve 6, adopts the intelligent combination of the circulating fluid frequency conversion speed regulation mode and the hot water supply adjustment mode, and comprehensively adjusts the target refrigerant water outlet temperature to achieve a combination The purpose of refrigeration and intelligent refrigeration (see Figure 4). This new lithium bromide absorption refrigeration unit can effectively improve the refrigeration efficiency of the lithium bromide absorption refrigeration unit driven by a low-temperature heat source, reduce the minimum driving heat source temperature required by the refrigeration unit, and promote its market promotion.

Embodiment two

As shown in Figure 5, a kind of refrigeration capacity adjustment method as described novel lithium bromide absorption refrigerating unit, comprises steps:

1) The PLC control system compares the actual temperature Tr of the target refrigerant water outlet of the evaporator 13 acquired by the evaporator outlet temperature transmitter 1 in real time with the set temperature Ts set by the touch screen display, the set temperature Ts is the target temperature of the refrigerant water outlet set by the user according to the external environment. This value is generally determined in conjunction with the thermal parameters of the unit design and the building heat load when the unit is running. In this embodiment, the default is 10°C;

2) If 1°C≤|Tr‐Ts|<5°C, the PLC control system first adopts the circulating fluid frequency conversion speed regulation mode, that is, calls the PID algorithm to adjust the inverter frequency, that is, when 5°C﹥Ts‐Tr≥1°C, The inverter performs PID adjustment to reduce the frequency; when 5℃﹥Tr-Ts≥1℃, the inverter performs PID adjustment to increase the frequency; then the inverter acts on the solution pump 16 connected to it, and the solution pump 16 controls the concentration of the dilute lithium bromide solution of the unit. Circulate the flow rate, and then adjust the cooling capacity until |Tr‐Ts|﹤1℃.

In this embodiment, if |Tr‐Ts|≥5°C, further steps are included:

3) Check the working status of the hot water electric control valve 6 and the frequency converter, judge the working status of the unit and the static time of the hot water electric control valve 6, so as to ensure that there will be no excessive adjustment and avoid frequent operation of the hot water electric control valve;

4) If the unit is not in full-load working condition and the hot water electric control regulating valve 6 has been static for 3 minutes, then start the hot water supply adjustment mode at the same time, that is, the PLC control system generates a signal, and the signal makes the hot water electric control adjust The opening of the valve 6 is increased or decreased by 5%. By optimizing the cooling capacity adjustment method, that is, the intelligent combination of circulating fluid frequency conversion speed regulation technology and hot water supply adjustment mode is used to comprehensively adjust the target refrigerant water outlet temperature and improve mediation efficiency. and precision;

5) Stand still for 3 minutes after the opening of the hot water electric control valve 6 is in place, then the PLC control system compares the actual temperature Tr of the target refrigerant water outlet of the evaporator 13 obtained by the evaporator outlet temperature transmitter 1 in real time with the actual temperature Tr through the touch screen If |Tr‐Ts| is less than 1°C, the adjustment of the cooling capacity is completed; otherwise, return to step 3), and continue to adjust the opening degree of the hot water electric control valve 6 until When |Tr‐Ts|﹤1℃, the cooling capacity adjustment is completed.

In this embodiment, when the actual temperature Tr is higher than the set temperature Ts, if the frequency of the inverter and the opening of the hot water electric control valve 6 have reached the upper limit, the unit maintains the current working state; when the actual temperature Tr is lower than the set temperature When the temperature is Ts, if the frequency of the inverter and the opening of the hot water electric control valve 6 have reached the lower limit, the PLC control system will start a yellow alarm signal, and at the same time the unit will stop, stop cooling and dilute, to protect the system from crystallization and other failures role.

In this embodiment, when the PLC control system generates a signal to control the opening of the hot water electric control valve 6, the hot water electric control valve 6 will timely feed back the current opening to the PLC control system through the closed-loop control system, and the PLC control According to the feedback data, the system judges and ensures that the hot water electric control valve 6 stops when it reaches the target opening, forming a closed-loop control to improve the adjustment accuracy of the hot water electric control valve.

The cooling capacity adjustment method provided in this embodiment comprehensively adopts the circulating fluid frequency conversion speed regulation mode and the hot water supply adjustment mode, optimizes the operation core part of the refrigeration unit, improves the circulation process of the lithium bromide solution, and because the circulating fluid frequency conversion speed regulation Mode is to change the working frequency of the inverter to adjust the cooling capacity. When the frequency drops to a certain level, the head of the solution pump will become too small and the cycle cannot be carried out, which is subject to certain restrictions. The use of hot water supply adjustment Mode, when the cooling capacity of the unit drops to 50% or below, the economy will drop significantly. Considering the advantages and disadvantages of the above two modes, the combined use of the two modes can achieve the cooling capacity adjustment target more effectively and economically without damaging the System stable operation characteristics. This adjustment method is suitable for solar absorption refrigeration systems driven by low-temperature hot water, thereby enhancing the cooling effect of solar air conditioners.

Finally, it should be noted that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (4)

1. A method for regulating the cooling capacity of a novel lithium bromide absorption refrigerating unit, said novel lithium bromide absorption refrigerating unit comprises a generator (10) and a condenser (12) arranged in a high-pressure chamber (11), a low-pressure The evaporator (13) and the absorber (14) in the cavity (15), the solar thermal collector circulation heating system that provides hot water for the generator (10), the solution heat exchanger (17), the PLC control system, The touch screen display connected to the PLC control system, the evaporator (13) is used to exchange heat with the target refrigerant water, and the solar heat collector circulation heating system includes solar heat collectors connected in sequence by pipelines to form a hot water circulation loop (5), hot water electric control valve (6), hot water pump (7), generator inlet temperature transmitter (8), flow transmitter (9), generator outlet temperature transmitter (4), The hot water electric control regulating valve (6), the generator inlet temperature transmitter (8), the flow transmitter (9), the generator outlet temperature transmitter (4) are all connected with the PLC control system circuit; Between said solution heat exchanger (17) and absorber (14), be provided with the solution pump (16) that lithium bromide dilute solution is pumped to generator (10) through solution heat exchanger (17), described solution The pump (16) is connected to the PLC control system circuit through a frequency converter; the target refrigerant water inlet pipeline of the evaporator (13) is provided with an evaporator inlet temperature transmitter (2), and the target of the evaporator (13) The refrigerant water outlet pipeline is provided with an evaporator outlet temperature transmitter (1); it also includes an ultrasonic strengthening device (3), and the transducer (18) of the ultrasonic strengthening device (3) is directly installed in the high pressure chamber ( 11) Bottom; the frequency of the ultrasonic strengthening device (3) is above 20kHz, and the working power is above 100w; the number of the transducers (18) is ≥ 1, and when the number exceeds 1, adjacent transducers (18) The distance between the installation positions is equal and not less than 100mm; a closed-loop control system is adopted between the hot water electric control regulating valve (6) and the PLC control system; it is characterized in that, comprising the steps: 1) The PLC control system compares the actual temperature Tr of the target refrigerant water outlet of the evaporator (13) acquired by the evaporator outlet temperature transmitter (1) in real time with the set temperature Ts set by the touch screen display; 2) If 1°C≤|Tr‐Ts|<5°C, the PLC control system first adopts the circulating fluid frequency conversion speed regulation mode, that is, calls the PID algorithm to adjust the frequency of the frequency converter, so that the frequency converter acts on the solution pump connected to it (16) , through the solution pump (16) to control the circulation flow rate of the lithium bromide dilute solution of the unit, and then adjust the cooling capacity until |Tr‐Ts|﹤1℃. 2. The cooling capacity adjustment method according to claim 1, characterized in that: if |Tr‐Ts|≥5°C, further comprising the steps of: 3) Check the working status of the hot water electric control valve (6) and frequency converter, and judge the working status of the unit and the static time of the hot water electric control valve (6); 4) If the unit is not in full-load working condition and the hot water electric control valve (6) has been static for 3 minutes, then start the mode of adjusting the hot water supply at the same time, that is, the PLC control system generates a signal, and the signal makes the hot water electricity The control valve (6) opening degree increases or decreases 5%; 5) After the opening of the hot water electric control valve (6) is in place, stand still for 3 minutes, and then the PLC control system will obtain the temperature of the target refrigerant water outlet of the evaporator (13) obtained in real time by the evaporator outlet temperature transmitter (1). The actual temperature Tr is compared with the set temperature Ts set through the touch screen display, if |Tr‐Ts|<1°C, the cooling capacity adjustment is completed, otherwise, return to step 3). 3. The cooling capacity adjustment method according to claim 2, characterized in that: when the actual temperature Tr is higher than the set temperature Ts, if the frequency of the inverter and the opening of the hot water electric control valve (6) have reached the upper limit, Then the unit maintains the current working state; when the actual temperature Tr is lower than the set temperature Ts, if the inverter frequency and the opening of the hot water electric control valve (6) have reached the lower limit, the PLC control system starts a yellow alarm signal, and the unit Shut down, stop refrigeration for dilution. 4. The cooling capacity adjustment method according to any one of claims 2 to 3, characterized in that: when the PLC control system generates a signal to control the opening of the hot water electric control valve (6), the hot water electric control adjusts The valve (6) feedbacks the current opening degree back to the PLC control system in time through the closed-loop control system, and the PLC control system judges and ensures that the hot water electric control regulating valve (6) stops when it reaches the target opening degree according to the feedback data, forming a closed-loop control.