CN102353403B - Methods for measuring chilled water flow and cooling medium flow of central air-conditioning host machine - Google Patents

Abstract

The invention belongs to the field of heating, ventilating and air-conditioning engineering and relates to a method for measuring chilled water flow of a central air-conditioning host machine. In the method, a linear relation between compressor actual input power and compressor theoretical input power is firstly established by utilizing factory test data or field measuring test data of the central air-conditioning host machine, and an adopted calculation method comprises the following steps of: (1) calculating the current flow of a refrigerant flow inside a refrigerating system of the central air-conditioning host machine; and (2) acquiring the flow of the chilled water of the central air-conditioning host machine according to a formula in the specification, wherein h11 represents an enthalpy value of the refrigerant at a condenser outlet, Cp represents the specific heat of the chilled water, T(evap,1) represents the temperature of a chilled water outlet of an evaporator of the central air-conditioning host machine, and T(evap,o) represents the temperature of a chilled water outlet of the evaporator of the central air-conditioning host machine. The invention simultaneously provides a method for measuring cooling medium flow of the central air-conditioning host machine. The methods disclosed by the invention are accurate and stable and has the advantage of greatly saving a large amount of instrument calibration and maintenance expenses compared with the traditional flowmeter.

Description

Central air conditioner main machine chilled-water flow and cooling medium consumption measuring method

Technical field

The invention belongs to Heating,Ventilating and Air Conditioning (HVAC) engineering field, be specifically related to a kind of measuring method for monitoring central air conditioner main machine chilled-water flow and cooling medium consumption.

Background technology

The chilled-water flow of central air conditioner main machine and cooling medium consumption monitored have great importance.The refrigeration system of central air conditioner main machine is generally carried out heat exchange with water or air as medium and cold-producing medium, suitable chilled-water flow and cooling medium consumption can guarantee that the refrigeration system of central air conditioner main machine is operated in state preferably, guarantee the work efficiency of unit.Unsuitable chilled-water flow and cooling medium consumption may cause the evaporator of air-conditioner host to freeze, condensing pressure raises, system's refrigerating efficiency descends.

Adopt flow instruments such as vortex shedding flow meter, ultrasonic flow meter, electromagnetic flowmeter for the water/air mass flow monitoring of central air conditioner main machine at present more.Price and the maintenance cost of above-mentioned flow instrument are high, and have certain requirement for mounting condition, and the distance that need satisfy upstream and downstream as the installation site of instrument is greater than the pipe diameter of several times.Expensive instrument price, maintenance cost and system's installation requirement have greatly limited flowmeter in actual application in engineering.

Summary of the invention

Fundamental purpose of the present invention is the deficiency that overcomes existing flow monitoring method, develops a kind of virtual flowmeter chilled-water flow and the cooling medium consumption of central air conditioner main machine are monitored.The present invention is based on the measured value of existing central air conditioner main machine sensor, utilize the method for modeling that chilled-water flow and the cooling medium consumption of central air conditioner main machine are predicted, thereby realize the flow of main frame refrigeration system is monitored, application is the hollow air-conditioner host, and its system should comprise evaporator, compressor, condenser and restriction device.Technical scheme of the present invention is as follows:

A kind of chilled water flow measuring method of central air conditioner main machine, this method at first utilize the delivery test data of central air conditioner main machine or in-site measurement experimental data to set up the actual power input (W of compressor _Ac) and the theoretical power input (W of compressor _Th) linear relationship, in actual measurement, adopt following computing method:

(1) according to the actual power input (W of the current compressor that records _Ac), calculate the theoretical power input (W of compressor _Th), according to formula

Obtain the refrigerant flow in the current central air conditioner main machine refrigeration system

In the formula, the cold-producing medium enthalpy h of the compressor outlet of central air conditioner main machine _DisAccording to the refrigerant temperature T of cold-producing medium character by compressor outlet _Dis, and condensing pressure P _CondDetermine; The cold-producing medium enthalpy h of the compressor inlet of central air conditioner main machine _SucAccording to the refrigerant temperature T of cold-producing medium character by compressor inlet _Suc, and condensing pressure P _EvapDetermine;

(2) chilled-water flow of central air conditioner main machine According to formula

Obtain, wherein, the cold-producing medium enthalpy h of condensator outlet _LlAccording to the refrigerant temperature T of cold-producing medium character by condensator outlet _LlWith condensing pressure P _CondDetermine; C _p: freezing specific heat of water; T _{Evap, i}: the chilled water inlet temperature of central air conditioner main machine evaporator; T _{Evap, o}: the chilled water outlet temperature of central air conditioner main machine evaporator.

As preferred implementation, a kind of chilled water flow measuring method of central air conditioner main machine is characterized in that, is setting up the actual power input (W of compressor _Ac) and the theoretical power input (W of compressor _Th) linear relationship the time, can determine the theoretical power input of compressor according to following formula: $W_{\mathrm{th}}=C_p\×[{\stackrel{\·}{m}}_{\mathrm{cond}}\×(T_{\mathrm{cond},i}-T_{\mathrm{cond},o})-{\stackrel{\·}{m}}_{\mathrm{evap}}\×(T_{\mathrm{evap},i}-T_{\mathrm{evap},o})],$ Also can determine the theoretical power input of compressor by formula: $W_{\mathrm{th}}={\stackrel{\·}{m}}_r\×(h_{\mathrm{dis}}-h_{\mathrm{suc}}).$

The present invention provides a kind of cooling medium consumption measuring method of central air conditioner main machine simultaneously, and this method at first utilizes the delivery test data of central air conditioner main machine or in-site measurement experimental data to set up the actual power input (W of compressor _Ac) and the theoretical power input (W of compressor _Th) linear relationship, in actual measurement, adopt following computing method:

(1) according to the actual power input (W of the current compressor that records _Ac), calculate the theoretical power input (W of compressor _Th), according to formula Obtain the refrigerant flow in the current central air conditioner main machine refrigeration system

In the formula, the cold-producing medium enthalpy h of the compressor outlet of central air conditioner main machine _DisAccording to the refrigerant temperature T of cold-producing medium character by compressor outlet _Dis, and condensing pressure P _CondDetermine; The cold-producing medium enthalpy h of the compressor inlet of central air conditioner main machine _SucAccording to the refrigerant temperature T of cold-producing medium character by compressor inlet _Suc, and condensing pressure P _EvapDetermine;

(2) cooling medium consumption of central air conditioner main machine

According to

With

Obtain, wherein, the cold-producing medium enthalpy h of condensator outlet _LlRefrigerant temperature T by condensator outlet _LlWith condensing pressure P _CondCalculate and obtain; C _p: the specific heat of heat eliminating medium; T _{Cond, o}: the heat eliminating medium outlet temperature of central air conditioner main machine condenser; T _{Cond, i}: the cooling medium inlet temperature of central air conditioner main machine condenser; T _{Evap, i}: the chilled water inlet temperature of central air conditioner main machine evaporator; T _{Evap, o}: the chilled water outlet temperature of central air conditioner main machine evaporator.

Before measuring, cooling medium consumption sets up the actual power input (W of compressor _Ac) and the theoretical power input (W of compressor _Th) linear relationship equally also can adopt two kinds of above-mentioned methods to determine the theoretical power input of compressor.

The present invention can be used for the chilled-water flow of central air conditioner main machine and cooling medium consumption are monitored, measured value based on existing central air conditioner main machine sensor, utilize the method for modeling that chilled-water flow and the cooling medium consumption of central air conditioner main machine are predicted, thereby realize chilled-water flow and the cooling medium consumption of main frame refrigeration system are monitored.Virtual stream measuring method of the present invention has following outstanding feature:

(1) experiment shows that this method measurement is accurate, stable;

(2) this method adopts the mode of virtual flow measurement, compares with traditional flowmeter and has saved a large amount of instrument calibrations and maintenance cost;

(3) this method adopts the mode of virtual flow measurement, does not have the restriction of installation requirement with traditional flowmeter system of comparing;

(4) this method cost performance is high, can monitor the flow of main frame vaporizer side and condenser side simultaneously, compares with traditional flowmeter and can save a large amount of initial costs.

Description of drawings

Fig. 1 is used for determining the central air conditioner main machine cooling cycle system figure of flow.

Embodiment

Fig. 1 is a typical central air-conditioner host Vapor Compression Refrigeration Cycle system 10.System 10 comprises cooling medium circulation system 20 and the chilled water circulation system 22.Enter condenser 14 after refrigerant vapour during refrigeration system work in the compressor 12 suction evaporators 18 is compressed.Cold-producing medium is cooled to liquid in equipressure under condensing pressure, and liberated heat is passed to heat eliminating medium if adopt water-cooling pattern during condensation of refrigerant, and heat eliminating medium is water, if adopt cooling air mode, heat eliminating medium is air.Condensed liquid enters evaporator 18 by restriction device 16.Cold-producing medium seethes with excitement under evaporating pressure, carries out heat exchange with chilled water.

As shown in Figure 1, a typical central air conditioner main machine should comprise with lower sensor: the refrigerant temperature T of compressor inlet _Suc, the refrigerant temperature T of compressor outlet _Dis, condensator outlet refrigerant temperature T _Ll, evaporating pressure P _Evap, condensing pressure P _Cond, cooling water inlet temperature T _{Cond, i}, cooling water outlet temperature T _{Cond, o}, chilled water inlet temperature T _{Evap, i}, the chilled water outlet temperature T _{Evap, o}, the actual power input W of compressor _Ac

The cooling medium consumption of central air conditioner main machine

And chilled-water flow

Can be determined by equation (1a) and equation (1b).

${\stackrel{\·}{m}}_{\mathrm{cond}}=\frac{{\stackrel{\·}{m}}_r\×(h_{\mathrm{dis}}-h_{\mathrm{ll}})}{c_p\×(T_{\mathrm{cond},o}-T_{\mathrm{cond},i})}---\left(1a\right)$

${\stackrel{\·}{m}}_{\mathrm{evap}}=\frac{{\stackrel{\·}{m}}_r\×(h_{\mathrm{suc}}-h_{\mathrm{ll}})}{c_p\×(T_{\mathrm{evap},i}-T_{\mathrm{evap},o})}---\left(1b\right)$

Used parameter interpretation is as follows in the equation:

: the cooling medium consumption of central air conditioner main machine;

: the refrigerant flow in the central air conditioner main machine refrigeration system;

h _Dis: the cold-producing medium enthalpy h of the compressor outlet of central air conditioner main machine _DisAccording to the refrigerant temperature T of cold-producing medium character by compressor outlet _Dis, and condensing pressure P _CondDetermine;

h _Ll: the cold-producing medium enthalpy h of condensator outlet _LlAccording to the refrigerant temperature T of cold-producing medium character by condensator outlet _LlWith condensing pressure P _CondDetermine;

C _p: the specific heat of water or air;

T _{Cond, o}: the heat eliminating medium outlet temperature of central air conditioner main machine condenser;

T _{Cond, i}: the cooling medium inlet temperature of central air conditioner main machine condenser;

: the chilled-water flow of central air conditioner main machine

h _Suc: the cold-producing medium enthalpy h of the compressor inlet of central air conditioner main machine _SucAccording to the refrigerant temperature T of cold-producing medium character by compressor inlet _Suc, and condensing pressure P _EvapDetermine;

T _{Evap, i}: the chilled water inlet temperature of central air conditioner main machine evaporator;

T _{Evap, o}: the chilled water inlet temperature of central air conditioner main machine evaporator.

In equation (1a) and equation (1b), except the refrigerant flow in the central air conditioner main machine refrigeration system

Be unknown quantity, other parameter all is known quantity, can directly be obtained by sensor reading.

Refrigerant flow in the central air conditioner main machine refrigeration system

Can be determined by equation (2):

${\stackrel{\·}{m}}_r=\frac{W_{\mathrm{th}}}{(h_{\mathrm{dis}}-h_{\mathrm{suc}})}---\left(2\right)$

Used parameter interpretation is as follows in the equation:

: the refrigerant flow in the central air conditioner main machine refrigeration system;

W _Th: the theoretical power input of compressor;

h _Dis: the cold-producing medium enthalpy h of the compressor outlet of central air conditioner main machine _DisAccording to the refrigerant temperature T of cold-producing medium character by compressor outlet _Dis, and condensing pressure P _CondDetermine;

h _Suc: the cold-producing medium enthalpy h of the compressor inlet of central air conditioner main machine _SucAccording to the refrigerant temperature T of cold-producing medium character by compressor inlet _Suc, and condensing pressure P _EvapDetermine;

In equation (2), remove the theoretical power input W of compressor _ThBe unknown quantity, other parameter is known quantity.

The theoretical power input W of compressor _ThCan be determined by equation (3):

W _th＝a×W _ac+b (3)

Used parameter interpretation is as follows in the equation:

W _Th: the theoretical power input of compressor;

W _Ac: the actual power input of compressor;

A and b: the fit equation coefficient, this coefficient can be obtained by following two kinds of methods.

Method 1: the delivery test data based on central air conditioner main machine are determined coefficient a and b.

The theoretical power input of the compressor of (at least four load conditions) can be determined one by one by equation (4) under the different load operating condition of test condition

$W_{\mathrm{th}}=C_p\×[{\stackrel{\·}{m}}_{\mathrm{cond}}\×(T_{\mathrm{cond},i}-T_{\mathrm{cond},o})-{\stackrel{\·}{m}}_{\mathrm{evap}}\×(T_{\mathrm{evap},i}-T_{\mathrm{evap},o})]---\left(4\right)$

Used parameter interpretation is as follows in the equation:

W _Th: the theoretical power input of compressor;

C _p: the specific heat of water or air;

: the cooling medium consumption of central air conditioner main machine;

T _{Cond, o}: the heat eliminating medium outlet temperature of central air conditioner main machine condenser;

T _{Cond, i}: the cooling medium inlet temperature of central air conditioner main machine condenser;

: the chilled-water flow of central air conditioner main machine;

T _{Evap, i}: the chilled water inlet temperature of central air conditioner main machine evaporator;

T _{Evap, o}: the chilled water outlet temperature of central air conditioner main machine evaporator.

W _Ac: the actual power input of compressor;

The actual input power measurement data W of compressor to (at least four load conditions) under the different load working condition _AcAnd by the theoretical power input data W of the definite compressor of equation (4) _ThCarry out match, then can determine coefficient a and b in the equation (3).

In addition, if the test figure of producer comprises the refrigerant temperature T of different load working condition lower compression machine outlet _DisRefrigerant temperature T with compressor inlet _Suc(30), the theoretical power input data W of the compressor in the equation (4) _ThAlso can be obtained by equation (5):

$W_{\mathrm{th}}={\stackrel{\·}{m}}_r\×(h_{\mathrm{dis}}-h_{\mathrm{suc}})---\left(5\right)$

Used parameter interpretation is as follows in the equation:

W _Th: the theoretical power input of compressor;

h _Dis: the cold-producing medium enthalpy h of the compressor outlet of central air conditioner main machine _DisAccording to the refrigerant temperature T of cold-producing medium character by compressor outlet _Dis, and condensing pressure P _CondDetermine;

h _Suc: the cold-producing medium enthalpy h of the compressor inlet of central air conditioner main machine _SucAccording to the refrigerant temperature T of cold-producing medium character by compressor inlet _SucAnd condensing pressure P (30), _EvapDetermine;

: the refrigerant flow in the central air conditioner main machine refrigeration system can utilize the cooling medium consumption of central air conditioner main machine

The heat eliminating medium outlet temperature T of central air conditioner main machine condenser _{Cond, o}The cooling medium inlet temperature T of central air conditioner main machine condenser _{Cond, i}The cold-producing medium enthalpy h of the compressor outlet of central air conditioner main machine _DisThe cold-producing medium enthalpy h of condensator outlet _LlCalculate definite etc. known parameters;

The actual input power measurement data W of compressor to (at least four load conditions) under the different load working condition _AcAnd by the theoretical power input data W of the definite compressor of equation (5) _ThCarry out match, then can determine coefficient a and b in the equation (3).

Method 2: determine coefficient a and b based on the in-site measurement experimental data.

For the unit of the delivery test data that central air conditioner main machine can't be provided, can determine coefficient a and b by the mode of in-site measurement.The in-site measurement parameter that needs is as follows:

: the cooling medium consumption of central air conditioner main machine;

: the chilled-water flow of central air conditioner main machine;

T _{Cond, o}: the heat eliminating medium outlet temperature of central air conditioner main machine condenser;

T _{Cond, i}: the cooling medium inlet temperature of central air conditioner main machine condenser;

T _{Evap, i}: the chilled water inlet temperature of central air conditioner main machine evaporator;

T _{Evap, o}: the chilled water inlet temperature of central air conditioner main machine evaporator;

W _Ac: the actual power input of compressor.

The actual input power measurement data W of compressor to (at least four load conditions) under the different load working condition _AcAnd by the theoretical power input data W of the definite compressor of equation (4) _ThCarry out match, then can determine coefficient a and b in the equation (3).

Similar with method 1, the theoretical power input data W of the compressor in the equation (4) _ThAlso can be obtained by equation (5).The actual input power measurement data W of compressor to (at least four load conditions) under the different load working condition _AcAnd by the theoretical power input data W of the definite compressor of equation (5) _ThCarry out match, then can determine coefficient a and b in the equation (3).

Claims (3)

1. the chilled water flow measuring method of a central air conditioner main machine, this method at first utilizes the delivery test data of central air conditioner main machine or in-site measurement experimental data to set up the actual power input W of compressor _AcAnd the theoretical power input W of compressor _ThLinear relationship, in actual measurement, adopt following computing method:

(1) according to the actual power input W of the current compressor that records _Ac, calculate the theoretical power input W of compressor _Th, according to formula

Obtain the refrigerant flow in the current central air conditioner main machine refrigeration system

In the formula, the cold-producing medium enthalpy h of the compressor outlet of central air conditioner main machine _DisAccording to the refrigerant temperature T of cold-producing medium character by compressor outlet _Dis, and condensing pressure P _CondDetermine; The cold-producing medium enthalpy h of the compressor inlet of central air conditioner main machine _SucAccording to the refrigerant temperature T of cold-producing medium character by compressor inlet _Suc, and condensing pressure P _EvapDetermine;

(2) chilled-water flow of central air conditioner main machine According to formula ${\stackrel{\·}{m}}_{\mathrm{evap}}=\frac{{\stackrel{\·}{m}}_r\×(h_{\mathrm{suc}}-h_{\mathrm{ll}})}{c_p\×(T_{\mathrm{evap},i}-T_{\mathrm{evap},o})}$ Obtain, wherein, the cold-producing medium enthalpy h of condensator outlet _LlAccording to the refrigerant temperature T of cold-producing medium character by condensator outlet _LlWith condensing pressure P _CondDetermine; c _p: freezing specific heat of water; T _{Evap, i}: the chilled water inlet temperature of central air conditioner main machine evaporator; T _{Evap, o}: the chilled water outlet temperature of central air conditioner main machine evaporator.

2. the chilled water flow measuring method of central air conditioner main machine according to claim 1 is characterized in that, is setting up the actual power input W of compressor _AcAnd the theoretical power input W of compressor _ThLinear relationship the time, determine the theoretical power input of compressor according to following formula:

$W_{\mathrm{th}}=c_p\×[{\stackrel{\·}{m}}_{\mathrm{cond}}\×(T_{\mathrm{cond},i}-T_{\mathrm{cond},o})-{\stackrel{\·}{m}}_{\mathrm{evap}}\×(T_{\mathrm{evap},i}-T_{\mathrm{evap},o})],$ In the formula,

: the cooling medium consumption of central air conditioner main machine;

T _{Cond, o}: the heat eliminating medium outlet temperature of central air conditioner main machine condenser;

T _{Cond, i}: the cooling medium inlet temperature of central air conditioner main machine condenser.

3. the chilled water flow measuring method of central air conditioner main machine according to claim 1 is characterized in that, is setting up the actual power input W of compressor _AcAnd the theoretical power input W of compressor _ThLinear relationship the time, determine the theoretical power input of compressor according to following formula:

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