Study of In Situ Performance of the VRF Multi-split Air Conditioner for the Commercial Building

Hirotaka Hanazaki（TEPCO Energy Partner, Inc.）Satoru Tanaka（Tokyo Electric Power Company Holdings, Inc.）Hirofumi Ida（ Tokyo Electric Power Company Holdings, Inc.）

Katsumi Hashimoto （ Central Research Institute of Electric Power Industry ）Katsuyuki Edahiro （ DAIKIN INDUSTRIES, LTD. ）

Toshihiro Oka（ DAIKIN INDUSTRIES, LTD. ） 1

BACKGROUND

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･The VRF system has been spreading extensively throughout Japan.

･However, there are few reports on measurement and evaluation of their performances in situ, due to difficulty of measuring the VRF system.

･On the other hand, measurement is a indispensable pursuit of energy conservation.

･In this research, we measured the VRF system in situ.And we did a study of the performance of the VRF system in situ using the refrigerant enthalpy (RE) method and the compressor curve (CC) method.

LOCATION

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Fig.2 The Building of TEPCO Research Institute

Fig.1 Japn map

◎2009 webmtabi.jp

the VRF system

MEASUREMENTLOCATION

The product under test was the VRF system installed in TEPCO Research Institute.

TESTING FACILITY

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Fig.3 The outdoor unit at the rooftop

Outdoor unit（※ The VRF system )

Fig.4 The indoor unit at laboratory

Indoor unit

MEASUREMENT

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Fig.5 The VRF system and a summary of the instruments installed around the refrigerant pipes

Table 1. Specifications of the VRF system

Instrument Measurement location during cooling

T-type thermocouple Surface temperature of liquid piping of outdoor unit [oC]

Surface temperature of vapor piping of outdoor unit [oC]

Pressure sensor [High pressure] Outdoor unit liquid line pressure [MPa]

[Low pressure] Outdoor unit vapour line pressure [MPa]

Coriolis flow meter Mass flow rate [kg/min] and density [kg/L] of liquid refrigerant

Power meter Electric power consumption [kW]

T-type thermocouple Atmospheric temperature

Hygrometer Atmospheric humidity

Table 2.The measured parameters

Instrument Outdoor Unit Indoor UnitNumber of Units 1 3Power supply Three-phase 200V,

50/60HzSingle-phase 200V,

50/60HzRated cooling capacity [kW/Unit] 28.0/28.0 11.2Rated cooling power consumption [kW/Unit] 8.58 0.165/0.194Rated heating capacity [kW/Unit] 31.5/31.5 12.5Rated heating power consumption [kW/Unit] 8.34 0.132/0.161Maximum low-temperature heating capacity[kW/Unit]

26.7/26.7 ―

Refrigerant R410A

＜REFERENCE＞Poster sessions P.3.1.2 Study of in Situ Monitoring Method for(Cooling and Heating) Capacity of Variable Refrigerant Flow (VRF) Multi-Split Air Conditioners for Commercial Buildings

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Fig.5 The VRF system and a summary of the instruments installed around the refrigerant pipes

＜REFERENCE＞Poster sessions P.3.1.2 Study of in Situ Monitoring Method for(Cooling and Heating) Capacity of Variable Refrigerant Flow (VRF) Multi-Split Air Conditioners for Commercial Buildings

In this research, the performance (capacity and COP) of the VRF system was estimated using the RE method and the CC method.

■The RE method

The RE method (refrigerant enthalpy method) estimates generated heat quantities (cooling capacity and heating capacity) by using the refrigerant mass flow and the refrigerant enthalpy difference between inlet and outlet of the outdoor unit.

■The CC method

The CC method is the compressor curve method. A manufacturer uses this method to understand actual performance of the VRF system.

MEASUREMENT METHOD

ASCERTAINING COOLING PERFORMANCE

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In this page, cooling performance is described.

The cooling capacity QC,CC and the coefficient of performanceCOPC,CC were estimated by the CC method from internal data from the VRF system.

QC,CC

COPC,CC

■The CC method → QC,CC COPC,CC

Cooling capacity QC,RE is estimated by the RE method.QC,RE

COPC,RE Coefficient of performance COPC,RE is calculated from the QC,RE and the measured power consumption

■The RE method → QC,RE COPC,RE

QC,RE and COPC,RE were compared with QC,CC and COPC,CC

＜REFERENCE＞Poster sessions P.3.1.2 Study of in Situ Monitoring Method for(Cooling and Heating) Capacity of Variable Refrigerant Flow (VRF) Multi-Split Air Conditioners for Commercial Buildings

ASCERTAINING COOLING PERFORMANCE

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X axis：Cooling capacity estimated by CC method, QC,CCY axis：The cooling capacity difference between measurement (RE method) and CC method

(QC,RE - QC,CC)

Fig.6 Comparison of Cooling Capacity Values Between the Measurement and the CC Method

① In the low load factor region,measurement value was larger than estimated value by CC method.

② In the high load factor region, the results show a slightly disparity within ±10% between the RE method estimated value and the CC method estimated value.

②①

Comparison of Cooling Capacity Values

ASCERTAINING COOLING PERFORMANCE

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Comparison of Power Consumption Values

①For power consumption, the measured value PRE was smaller than internal data PCC for the whole range. PRE was lower than PCC by 0.3~0.5kW over the whole range.

Fig.7 Comparison of Power Consumption Values

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X axis： Cooling capacity estimated by CC method, QC,CCY axis：The difference between the measured power consumption value, PRE, and

the power consumption value estimated by the CC method, PCC

ASCERTAINING COOLING PERFORMANCE

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①For COP, measurement is larger than CC method estimated value over the whole range. The divergence between Measurement and CC method estimated value was particularly large in the low load factor region.

Fig.8 COP Comparison

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COP Comparison

X axis： Cooling capacity estimated by CC method, QC,CC,Y axis：The difference between Measurement and CC method estimates of COP,

(COPC,RE - COPC,CC)

ASCERTAINING COOLING PERFORMANCE

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①In the high load factor region, COPC,RE is close to the catalog value of 3.26 (*rated cooling capacity/rated power consumption)

② COPC,RE increased as load factor approached 30% in the low load factor region.

Fig.9 Relationship Between Load Factor and COP

※COP3.26

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②

Ascertaining COP Under Partial Load

X axis：Load factor (=instantaneous output / rating capacity)Y axis：Cooling COP (Measurement)

Ascertaining COP Under Partial Load

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① The lower the load factor, the lower the power consumption.

②In the 0.2～0.9 load factor range, power consumption is smaller than the straight line between 0 and the rated power consumption 8.58kW.

Fig.10 Relationship Between Load Factor and power consumption in Cooling

The straight line connected 0 with the rated power consumption 8.58kW

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②

Relationship Between Load Factor and Power Consumption

X axis：Load factor (=instantaneous output / rating capacity)Y axis：Power consumption (Measurement)

ASCERTAINING HEATING PERFORMANCE

8.58kW

CONCLUSION

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･In this research, the measurement of the VRF system was successfully conducted. And the cooling performances (cooling capacity ,cooling load factor and cooling COP) could be estimated by the RE method and the CC method .

Measurement･The performances by the RE method are compared with one by the CC method

･While measurement accuracy by RE method is high, simplification is necessary toimprove usability.

Performance of VRF system･In the high load factor region, COPC,RE is close to the catalog value of 3.26 (*rated cooling capacity/rated power consumption)

･Cooling COP increased as cooling load factor decreased. It is confirmed that theimprovement of the VRF system is achieved properly.