KR20040042733A - Method for analysis of efficiency in turbo refrigerator and apparatus thereof - Google Patents

Abstract

PURPOSE: A method and an apparatus for analyzing the performance of a turbo freezer are provided to analyze and predict the performance of a freezer on given random conditions. CONSTITUTION: A freezing cycle(10) includes a compressor(11), a condenser(12), an expander(13), and an evaporator(14). Temperature measuring elements(21,22) are installed at heat dissipating water inlet and outlet. Other temperature measuring elements(31,32) are installed at heat absorbing water inlet and outlet. A flux measuring element(23) is installed at the heat dissipating water inlet or outlet. Another flux measuring element(33) is installed at the heat absorbing water inlet or outlet. A power consumption measuring element(15) is installed at the compressor for measuring power consumption. Pressure measuring elements(16,17) are installed at the condenser and the evaporator. An analyzing element(40) is connected with the temperature measuring elements, the flux measuring element, the power consumption measuring element, and the pressure measuring elements for processing the measured values.

Description

METHOD FOR ANALYSIS OF EFFICIENCY IN TURBO REFRIGERATOR AND APPARATUS THEREOF

The present invention relates to a turbo chiller, and more particularly, to a method and apparatus for analyzing and predicting the performance of a chiller under any given conditions, such as the flow rate of radiant and endothermic water, temperature, power consumption of a compressor, etc. It is about.

Today, the issue of resource depletion and environmental pollution has risen, and interest in energy saving has been increasing all over the world for a long time.

In particular, in recent years, the government has actively invested in energy-saving matters such as establishing an energy service company (ESCO) system and strengthening support for the target companies in order to effectively promote energy-saving projects. And focusing efforts.

In order to operate the energy saving business more efficiently, the process of properly understanding the energy use of the heat source and the air conditioning system currently used must be preceded, and for this purpose, an accurate diagnosis of the refrigeration system operating in the field is first of all necessary.

Refrigerators used in air conditioning systems to handle cooling loads in buildings and factories can be said to have high power consumption and a high potential for improvement.

In particular, the turbo chiller can save a lot of energy by proper design, selection, installation and maintenance. Unlike a small refrigeration system that is sold and installed in one-piece form, it is installed as part of a heat source device in the whole air conditioning system, so the operating temperature of the radiant water and the endothermic water as well as the radiant water, endothermic pump, air conditioner, and piping conditions This is because there are many variables that can affect the performance, such as the flow rate may flow differently from the reference conditions.

In addition, even after installation of the turbo refrigerator, the performance of the air conditioning system can be improved by changing the flow rate of the radiant water or the endothermic water.

In practice, when measuring the performance of a refrigerator installed on site, it is often impossible to obtain performance test data under standard conditions specified by regulation by arbitrarily adjusting the temperature and flow rate of radiant or absorbent water. Because of the control characteristics, the freezer operates abnormally, so the performance analysis in the quasi-steady state should be performed.

Therefore, there is an urgent need to develop a model that can predict the performance of a refrigerator under arbitrary temperature and flow conditions by using performance data of a quasi-steady state of a refrigerator installed and operating in the field.

The present invention solves the problems as described above, and the turbo chiller to analyze and predict the performance of the refrigerator under any given conditions, such as the flow rate of the radiant and endothermic water, temperature, power consumption of the compressor, etc. It is an object of the present invention to provide a performance analysis method and apparatus.

1 is a block diagram showing the configuration of the performance analysis apparatus according to the present invention

Figure 2 is a graph comparing the performance coefficient of the freezer obtained by the actual experiment with the performance coefficient of the freezer predicted by the performance analysis method according to the present invention

FIG. 3 is a graph illustrating comparison of dimensionless values as performance coefficients of a refrigerator obtained by actual experiments with dimensionless values as performance coefficients of a refrigerator predicted by the performance analysis method according to the present invention.

** Description of the symbols for the main parts of the drawings **

10 refrigeration cycle 11 compressor

12 condenser 13 expander

14 evaporator 15 power measurement means

16 pressure measuring means 17 pressure measuring means

20: cooling tower 21: heat radiation water inlet temperature measuring means

22: radiating water outlet temperature measuring means 23: radiating water flow rate measuring means

30: freezing target unit 31: endothermic water inlet temperature measuring means

32: endothermic water outlet temperature measuring means 33: endothermic water flow rate measuring means

40: analysis means

The present invention is to provide a model that can be equipped with a measuring means in the minimum portion of the turbo freezer in the field for collecting data necessary for performance analysis of the refrigerator, and predict the performance coefficient of the turbo freezer from the experimental data obtained from the measuring means. will be.

In general, since there are no detailed specifications or performance data of a compressor or heat exchanger of a turbo refrigerator installed in the field, it is a reality that individual device characteristics of the turbo refrigerator are not predicted or performance deterioration due to long-term operation.

In addition, the experimental data necessary for the prediction of the coefficient of performance is not obtained by changing the arbitrary conditions in the laboratory scale experimental apparatus, but is made on the premise of the refrigeration load and the atmospheric condition in the state of being installed and operated in the field. Since it is necessary to obtain, it is very difficult to obtain a wide range of experimental data due to changes in various conditions. Therefore, appropriate modeling is needed to predict the performance of turbo chillers from limited experimental data obtained in the field.

In modeling, it would be ideal to consider individual specifications for each turbocooler. However, due to the lack of specification data and experimental data, it is impossible to obtain satisfactory results because appropriate values of coefficients required for tuning the model cannot be obtained.

Therefore, the present invention designates the condensation temperature, the evaporation temperature, the capacity of the discharged water and the endothermic water, and the freezing capacity as variables, which are the factors that have the most decisive influence on the performance of the refrigeration system, and applies a second law of thermodynamics to a relatively simple method. By suggesting a model that can analyze and predict the coefficient of performance of the refrigerator from the relationship between the variables.

The performance analysis system of a turbo-cooler according to the present invention includes a performance analysis apparatus including measurement means for obtaining data and analysis means for processing the collected data, and a performance analysis method for processing the obtained data by analysis means. Since it can be expressed in two categories, hereinafter, the configuration of the performance analysis device will be described, and then the analysis method performed in the device will be described in detail.

1 is a block diagram showing the configuration of a performance analysis device for a turbo-frigerator according to the present invention.

As shown, performance analysis of a turbo chiller according to the present invention basically comprises a refrigeration cycle (10) comprising a compressor (11), a condenser (12), an expander (13) and an evaporator (14), and a condenser (12). And a radiant water outlet and an inlet formed to flow in and out of the radiant water between the cooling tower 20 and a endothermic water outlet and an inlet formed to flow and enter the endothermic water between the evaporator 14 and the freezing target unit 30. It is used to analyze the performance of a turbocooler.

Temperature measuring means (21, 22) is mounted on the heat radiation water inlet and outlet for performance analysis according to the present invention, and temperature measuring means (31, 32) are also mounted on the heat absorbing water inlet and outlet, and the heat radiation water inlet Alternatively, the outlet is equipped with a flow rate measuring means 23, the endothermic water inlet or outlet is equipped with a flow rate measuring means 33, the compressor 11 power consumption measuring means 15 for measuring the power consumption thereof. The pressure condenser 12 and the evaporator 14 are equipped with pressure measuring means 16 and 17, respectively.

In addition, analysis means for processing values obtained from the temperature measuring means (21, 22, 31, 32), flow rate measuring means (23, 33), power consumption measuring means (15) and pressure measuring means (16, 17). 40 is provided and is electrically connected with each said measuring means.

Here, the temperature measuring means (21, 22, 31, 32) can be easily implemented by a thermocouple, a platinum resistance temperature sensor, a thermopile, a thermowell in which a platinum resistance temperature sensor is inserted, and the like. The flow rate measuring means 23 and 33 may be implemented by an ultrasonic flow meter or the like, and the power consumption measuring means 15 may include a measuring unit of current, voltage, and power factor applied to the motor of the compressor 11. The analyzing means 40 may be implemented by a computer which allows data obtained from the measuring means to be input and processed by a method as described below.

Each measurement value is stored in the analysis means 40 at intervals of less than one minute so as to interpret abnormal behavior of the refrigerator.

Hereinafter, as a method of analyzing the variation of the performance coefficient of the refrigerator according to the variation of each variable (temperature, flow rate, etc.) from the data obtained from the measuring means, two methods will be presented.

First, a method of predicting the performance coefficient from the freezing capacity, the radiant water inlet temperature, and the endothermic water outlet temperature will be described.

The refrigerating capacity can be obtained by the following equation from the measured endothermic flow rate and temperature difference between the inlet and outlet (inlet and outlet of the evaporator).

Q _e : Refrigeration capacity m _ew : Endothermic flow rate

C _pw : Specific heat of water T _ewi : Evaporator inlet temperature

T _ewo : evaporator outlet temperature

Since the cooling load and the outside air temperature change with time, the temperature of the radiant and endothermic water flowing into the refrigerator is also changed. Accordingly, the partial load operation of the refrigerator and the control of the cooling tower are performed. Power, freezer pressure, etc. will also show periodic fluctuations. Therefore, the data is processed assuming that the time-averaged value by integrating at intervals of 10 minutes or more is assumed as the representative value of the time.

Equation 2 can be obtained by applying the first law of thermodynamics to a refrigeration system.

Q _c : Heat dissipation Q _e : Refrigeration capacity

W: power consumption of the compressor

In the refrigeration system, irreversibility occurs due to fluid friction, heat transfer, etc., about 50% of the irreversibility generated in the whole system is made in the compressor, and the rest is exchanged with the secondary fluid in the condenser and evaporator, expansion valve, condenser Pressure drop in the evaporator, refrigerant pipe, or the like.

Since irreversibility of pressure drop is negligible, the irreversibility generated by the compressor and the irreversibility generated by heat exchange with the heat source in the condenser and the evaporator occupy most of them.

Except for the case of heat exchange with the secondary fluid, when considering only the irreversibility generated inside, the internal generated entropy is expressed as in Equation 3.

Q _c : Heat dissipation Q _e : Refrigeration capacity

T _cr : Condensation temperature _Ter : Evaporation temperature

ΔS _int : internally generated entropy

The temperature of the refrigerant may be defined using the relationship T = Δh / Δs, but in practice it is not constant due to the presence of overheating and subcooling zones, so from the measured saturation temperature of the pressure of the condenser and evaporator Applying the calculated values is desirable in terms of facilitating the processing of experimental data.

The heat transfer process in the condenser and the evaporator can be represented by equations (4) and (5).

Q _c : Heat dissipation T _cr : Condensation temperature

T _cwi : radiant water inlet temperature

Q _e : Refrigeration capacity T _ewo : Endothermic water outlet temperature

_Ter : Evaporation Temperature

Here, since the temperature of the refrigerant is constant, heat exchanger availability E and E 'are defined by equations (6) and (7).

The coefficient of performance of the refrigerator is defined as in Equation 8.

Q _e : Refrigeration capacity W: Power consumption of compressor

The coefficient of performance of the refrigerator from Equations 2 to 5 is derived as shown in Equation (9).

By rearranging Equations 4 and 5, Equations 10 and 11 can be obtained.

Here, ΔT _max and ΔT _min mean the maximum temperature difference and the minimum temperature difference between the refrigerant and the secondary fluid, respectively.

By roughly summarizing the equation (9) using equations (10, 11), equation (12) can be obtained.

In the case of reciprocating chillers, the freezing capacity and the coefficient of performance of the refrigerator are given as a function of the condensation and evaporation temperatures of the refrigerant, so the internally generated entropy can also be assumed as a function of the condensation and evaporation temperatures.

However, in the case of a turbo refrigerator, it is possible to control the refrigerating capacity by adjusting the IGV at the same condensation temperature and the evaporation temperature, and the coefficient of performance also has a different value depending on the refrigerating capacity. .

On the other hand, since the internal irreversibility is caused by the friction of the fluid, it can be said that as the fluid flow rate increases, that is, as the refrigeration capacity increases.

In the case of a turbo refrigerator, the freezing capacity is controlled so that the outlet temperature of the endothermic water, which is the evaporator secondary fluid, is kept constant, and the amount of heat emitted from the cooling tower according to the freezing capacity is maintained so that the inlet temperature of the radiant water, which is the secondary fluid of the condenser, is kept constant. Controlled. Therefore, it can be assumed that the internally generated entropy in the turbo refrigerator is proportional to the freezing capacity.

In addition, since the irreversibility generated by heat transfer with the heat source in the condenser and the evaporator neglected in the approximation process of Equation 12 is also proportional to the heat transfer, it can be said that such irreversibility also increases in proportion to the freezing capacity.

Therefore, assuming that the production entropy of the entire refrigeration system is substituted for the internal irreversibility of Equation 12, and the total production entropy has a linear proportionality to the freezing capacity, Equation 13 can be obtained.

Here, the coefficients C ₁ and C ₂ are obtained using the least-squares method using field performance test data. The coefficients C ₁ and C ₂ obtained by the measured values represent the performance characteristics of the refrigerator in actual operation in the field and have different values for each refrigerator.

That is, when the freezing capacity, the endothermic water inlet temperature, the radiant water outlet temperature, and the performance coefficient obtained by the process as described above are substituted into Equation 13 and two coefficients are determined by the least error square method, Equation 13 is determined. By using, we can analyze and predict the variation of performance coefficient according to the variation of each variable (refrigeration capacity, endothermic inlet temperature, radiant water outlet temperature), and conversely, It is also possible to predict power consumption.

2 is a graph showing a comparison of the performance coefficient of the refrigerator (X-axis) obtained by the actual experiment with the performance coefficient (Y-axis) of the refrigerator predicted by the performance analysis method according to the present invention.

The measured values were measured from June to September for the same refrigerator for verification of the model, and 488 points of experimental data were applied except for the data at the initial start and stop of the refrigerator.

It can be seen that the experimental value and the predicted value of the coefficient of performance coincide within the error range of 5% even in the periodic normal operation state instead of the normal state.

Second, a description will be given of a method for predicting the performance coefficient from the refrigeration capacity, the radiant water inlet temperature, the endothermic water outlet temperature, the radiant water flow rate, and the endothermic water flow rate.

Equations 1 to 8 are the same as in the case of the first method.

However, in the condenser and evaporator models represented by Equations 4 and 5, the total heat transfer coefficient UA uses the relationship of Equations 14 and 15 represented by the flow rate and the heat transfer amount of the secondary fluid.

Here, the thermal resistance due to the secondary fluid contamination cannot be accurately predicted, but the allowable contamination coefficient of the condenser is 0.000086㎡ ℃ / W, which has a relatively small value compared to the refrigerant and the secondary fluid side heat resistance. It was not included independently in the calculation of the total heat transfer coefficients for the treatment of, but instead included in the section on the heat transfer resistance of refrigerants and secondary fluids.

The coefficients C ₃ , C ₄ , C ₅ and C ₆ are obtained using the least-squares method using field performance test data.

Once the coefficients are determined, the simulated total heat transfer coefficients UA _c and UA _c of the condenser and the evaporator can be obtained by substituting an arbitrary value into each variable of Equations 14 and 15, and the calculated total heat transfer coefficients are represented by Equation 16, 17, and the simulated condensation temperature and the simulated evaporation temperature of the refrigerant can be calculated by substituting the values E _c , E _e ', the endothermic water outlet temperature, and the radiant water inlet temperature obtained in Equation 4,5.

On the other hand, the irreversibility of the refrigeration system is defined as a function of the freezing capacity as shown in Equation 18.

Here, the coefficients C ₇ , C ₈ , and C ₉ are obtained using the least-squares method using field performance test data.

Substituting the simulation condensation temperature, simulation evaporation temperature and simulation internal entropy obtained by the above process into Equations 2, 3, and 8 can simulate the power consumption and simulation performance coefficient of the compressor.

That is, the simulation total heat transfer coefficient and simulation internal entropy are obtained by substituting an arbitrary value into each variable of Equations 14, 15, and 18 in which the coefficients are determined, and the obtained simulation total heat transfer coefficient, endothermic water outlet temperature, and radiant water inlet temperature. To the equations (16), (17), and (4) and (5) sequentially to obtain the simulated condensation temperature and the simulated evaporation temperature of the refrigerant, and the generated internal entropy, the simulated condensation temperature, and the simulated evaporation temperature of the refrigerant (2, 3). By substituting Equation 8, we obtain the simulation power consumption and simulation performance coefficients to analyze the variation of the performance coefficient according to the variation of each variable.

FIG. 3 shows a comparison between the non-dimensionalized value (X-axis) as the coefficient of performance of the refrigerator obtained by actual experiments and the non-dimensionalized value (Y-axis) as the coefficient of performance of the refrigerator predicted by the performance analysis method according to the present invention. One graph.

The measured values were measured from June to September for the same refrigerator for verification of the model, and rated full load conditions (absorbent water outlet temperature 7 ℃, radiant water inlet temperature 32 ℃, refrigeration capacity 703㎾) The coefficient of performance at is shown as dimensionless.

It can be seen that the experimental value and the predicted value of the coefficient of performance coincide within the error range of 5%.

In addition, when the model is used, performance analysis and prediction according to temperature change of the endothermic water and the radiant water, performance analysis and prediction according to the flow rate change of the endothermic water and the radiant water are possible.

The present invention provides a method and apparatus for analyzing the performance of a turbo-cooler, which enables to analyze and predict the performance of the refrigerator under any given conditions, such as the flow rate, temperature, power consumption of the compressor, and the like of the radiator and endotherm of the turbo-cooler installed in the field. .

Claims (10)

A refrigeration cycle including a compressor, a condenser, an expander, and an evaporator, a radiant water outlet and an inlet configured to discharge and introduce radiant water between the condenser and the cooling tower, and endothermic water between the evaporator and the refrigeration target portion; A method for analyzing the performance of a turbo chiller having an endothermic water outlet and an inlet formed, Measuring the temperature of the endothermic water inlet and outlet; Measuring a temperature of the heat radiation water inlet; Measuring a flow rate of the endothermic water; Measuring power consumption of the compressor; Obtaining a freezing capacity by substituting the endothermic water inlet temperature, the endothermic water outlet temperature, and the endothermic water flow rate into Equation 1; Obtaining a coefficient of performance by substituting the refrigeration capacity and power consumption into Equation 8; Determining two coefficients by the least error square method by substituting the refrigeration capacity, the endothermic water inlet temperature, the radiant water outlet temperature, and the performance coefficient into Equation (13); Analyzing the variation of the performance coefficient according to the variation of each variable using Equation 13 in which the coefficient is determined; Performance analysis method of the turbo-chiller comprising. A refrigeration cycle including a compressor, a condenser, an expander, and an evaporator, a radiant water outlet and an inlet configured to discharge and introduce radiant water between the condenser and the cooling tower, and endothermic water between the evaporator and the refrigeration target portion; A method for analyzing the performance of a turbo chiller having an endothermic water outlet and an inlet formed, Measuring the temperature of the endothermic water inlet and outlet; Measuring a temperature of the heat radiation water inlet; Measuring a flow rate of the endothermic water; Measuring a flow rate of the radiant water; Measuring power consumption of the compressor; Measuring the pressure of the condenser and the evaporator; Obtaining a freezing capacity by substituting the endothermic water inlet temperature, the endothermic water outlet temperature, and the endothermic water flow rate into Equation 1; Calculating a heat dissipation amount by substituting the refrigeration flow rate and power consumption into Equation 2; Obtaining a condensation temperature from the saturation temperature of the condenser pressure; Obtaining a compression temperature from the saturation temperature of the evaporator pressure; Obtaining a total heat transfer coefficient of the condenser by substituting the heat radiation amount, heat radiation flow rate, heat radiation water inlet temperature, and condensation temperature into Equations 4 and 6; Obtaining the total heat transfer coefficient of the evaporator by substituting the refrigeration capacity, the endothermic water flow rate, the endothermic water outlet temperature, and the compressed temperature into Equations 5, 6, and 7; Determining two coefficients by the least error square method by substituting the total heat transfer coefficient, the radiant water flow rate, and the radiant amount of the condenser into Equation 14; Determining two coefficients by the least error square method by substituting the total heat transfer coefficient, the endothermic flow rate, and the freezing capacity of the evaporator into Equation 15; Obtaining an internal generated entropy by substituting the heat dissipation amount and the freezing capacity into Equation 3; Determining two coefficients by the least-squares method by substituting the internally generated entropy and the freezing capacity into Equation 18; Obtaining a simulated total heat transfer coefficient and a simulated internal generation entropy by substituting an arbitrary value to each variable of Equations 14, 15, and 18 in which the coefficients are determined; Calculating the simulated condensation temperature and the simulated evaporation temperature of the refrigerant by sequentially substituting the simulated total heat transfer coefficient, the endothermic water outlet temperature, and the radiant water inlet temperature into Equations 16, 17, and Equations 4 and 5; By calculating the simulation power consumption and simulation performance coefficients by substituting the internal simulation entropy, simulation condensation temperature, and simulation evaporation temperature into Equations 2, 3, and 8, the process of analyzing the variation of the performance coefficient according to the variation of each variable ; Performance analysis method of the turbo-chiller comprising. A performance analysis apparatus for implementing the performance analysis method of the turbo chiller of claim 1, Temperature measuring means mounted to said endothermic water inlet and outlet and said radiant water inlet; Flow measurement means mounted to the endothermic water inlet or outlet; Flow rate measuring means mounted to the inlet or outlet of the radiant water; Power consumption measuring means mounted to the compressor; Analyzing means for analyzing the variation of the performance coefficient according to the variation of each variable by processing the values obtained from the temperature measuring means, the flow rate measuring means and the power consumption measuring means by the performance analysis method of claim 1; Performance analysis device of the turbo-chiller comprising. A performance analysis apparatus for implementing the performance analysis method of the turbo chiller of claim 2, Temperature measuring means mounted to said endothermic water inlet and outlet and said radiant water inlet and outlet; Flow measurement means mounted to the endothermic water inlet or outlet; Flow rate measuring means mounted to the inlet or outlet of the radiant water; Power consumption measuring means mounted to the compressor; Pressure measuring means mounted to the condenser and the evaporator, respectively; Analyzing means for analyzing the variation of the performance coefficient according to the variation of each variable by processing the values obtained from the temperature measuring means, the flow rate measuring means, the power consumption measuring means, and the pressure measuring means by the performance analysis method of claim 2; Performance analysis device of the turbo-chiller comprising. The method according to claim 3 or 4, The temperature measuring means is a performance analysis device of the turbo-freezer, characterized in that the thermocouple. The method according to claim 3 or 4, The temperature measuring means is a performance analysis device of a turbo refrigerator, characterized in that the platinum resistance temperature sensor. The method according to claim 3 or 4, The temperature measuring means is a performance analysis device of the turbo-cooler, characterized in that the thermopile. The method according to claim 3 or 4, The temperature measuring means is a performance analysis device of a turbo-cooler, characterized in that the thermowell with a platinum resistance temperature sensor is inserted. The method according to claim 3 or 4, The flow rate measuring means is a performance analysis device of the turbo-cooler, characterized in that the ultrasonic flow meter. The method according to claim 3 or 4, The power consumption measuring means includes a performance analysis device for a turbo chiller, characterized in that for measuring the current, voltage and power factor applied to the motor of the compressor.