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SCIENCE CHINA Technological Sciences, Volume 61 , Issue 12 : 1814-1823(2018) https://doi.org/10.1007/s11431-017-9237-6

Experimental research on the heating performance of a single cylinder refrigerant injection rotary compressor heat pump with flash tank

JinFei SUN 1,2,3,4, DongSheng ZHU 1,2,3,*, YingDe YIN 1,2,3, XiuZhen LI 1,2,3,4
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  • ReceivedSep 10, 2017
  • AcceptedMar 19, 2018
  • PublishedMay 11, 2018

Abstract

A single cylinder rotary compressor was applied in the refrigerant injection air-source heat pump to improve the heating performance in cold regions. In this study, the performance of an R410A single cylinder rotary compressor vapor injection (SCRCVI) system was measured and analyzed by varying the compressor frequency f and injection pressure Pinj at the ambient temperature Tod=–10°C.The experimental results indicated that an optimum injection pressure to gain the maximum COPh (coefficient of performance) existed in the SCRCVI cycle. However, the maximum COPh of the SCRCVI system decreased as the increase of the frequency, and the maximum COPh was even lower than that of the CSVC system at high compressor frequency. Therefore, in view of the energy saving and emission reduction, the SCRCVI system should be switched to single stage compression system when the heating capacity demand could be satisfied at high compressor frequency f. Compared to the conventional single-stage vapor compression (CSVC) system, refrigerant injection could enhance the heating capacities and COPh by 28.2% and 7.91%, respectively. The average total mass flow rate of the SCRCVI system was 24.68% higher than that of the CSVC system. As the SCRCVI system worked at the optimum injection pressure, the variation trends of the different system parameters were investigated in detail. These trends were reliably used to optimize the refrigerant injection system design and the control strategy. The parameter of (PinjPs) could be adopted as the signals to control the opening of the upper stage electronic expansion valve EEV1.


Funded by

the South Wisdom Valley Innovative Research Team Program(serial,number:,Shunde,District,of,Foshan,City,Government,Office,[2014],No.365)

the 2017 Guangzhou Collaborative Innovation Major Projects(Grant,Nos.,201604016048,&,201604016069)


Acknowledgment

This work was supported by the South Wisdom Valley Innovative Research Team Program (serial number: Shunde District of Foshan City Government Office [2014] No.365) and the 2017 Guangzhou Collaborative Innovation Major Projects (Grant Nos. 201604016048 and 201604016069).


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  • Figure 1

    Structure of rotary compressor.

  • Figure 2

    Schematic diagram of working process in cylinder. (a) Suction; (b) injection & compression; (c) compression; (d) discharge.

  • Figure 3

    Schematic diagram of the experimental setup.

  • Figure 4

    Pressure-enthalpy diagram.

  • Figure 5

    Variation of heating capacity with injection pressure.

  • Figure 6

    Variation of power consuming with injection pressure.

  • Figure 7

    Variation of COPh with injection pressure.

  • Figure 8

    Variation of total mass flow rate with injection pressure.

  • Figure 9

    Variation of discharge temperature with injection pressure.

  • Figure 10

    Variation of discharge pressure and suction pressure with compressor frequency.

  • Figure 11

    Variation of discharge temperature with compressor frequency.

  • Figure 12

    Variation of Rm and Rp with compressor frequency.

  • Figure 13

    Variation of optimum injection pressure and (PinjPs) with compressor frequency.

  • Table 1   Variation of the working chamber pressure

    Processes

    Specifications

    Suction

    Pinj > Pwc

    Refrigerant injection

    Pinj > Pwc

    Compression

    PinjPwc

    Discharge

    Pwc = Pdis

  • Table 2   Specification of system components.

    Components

    Specifications

    Compressor

    Type: inverter driven rotary compressor; displacement volume: 10.8 cm³ rev–1; the circle radius of cylinder: 21.5 mm; the rotor radius: 17.05 mm; the length of the cylinder: 20 mm; the diameter of injection hole: 4 mm

    Condenser (indoor heatexchanger)

    Type: fin/tube heat exchanger (aluminum/copper), L-shaped; tube outer diameter: Ø6.14×0.57 mm; fin thickness: 0.1 mm; fin spacing: 1.2 mm; number of rows: 2; number of tubes: 34; dimension:700 mm×360 mm×26 mm

    Evaporator (outdoor heatexchanger)

    Type: fin/tube heat exchanger (aluminum/copper), L-shaped; tube outer diameter: Ø9.52×0.7 mm; fin thickness: 0.1 mm; fin spacing: 1.1 mm; number of rows: 2; number of tubes: 40; dimension: 880 mm×510 mm×45 mm

    Electrical expansion valve

    Type: electronic expansion valve control resolution: 0–500 steps

    flash tank

    outer diameter: 38.32 mm; volume: 185 cm³

  • Table 3   Experiment conditions

    Operating mode

    Indoor

    Outdoor

    TDB (°C)

    TWB (°C)

    TDB (°C)

    TWB (°C)

    Heating

    20

    15

    −10

    -

    Refrigerant type

    R410A

     

    Refrigerant charge

    1380 g

     

    Compressor frequency f

    60–100 Hz

     

    Superheated degree of the suction vapor

    3–5 K

     
  • Table 4   Instrumentation and propagated uncertainties

    No.

    Instrument

    Type

    Range

    Uncertainty

    Obtaining data

    1

    Thermocouple

    T

    –200°C–350°C

    ±0.5°C

    Measured value (refrigerant-side)

    2

    Pressure transducer

    Ceramic membrane

    0–4000 kPa

    ±0.2% of full scale

    Measured value (refrigerant-side)

    3

    Pressure transducer

    Ceramic membrane

    0–6000 kPa

    ±0.2 % of full scale

    Measured value (refrigerant-side)

    4

    Temperature sensor

    platinum thermistor

    –50°C–300°C

    ±0.15°C

    Measured value (air-side)

    5

    Pressure difference transducer

    Diaphragm

    0–6 bar

    ±0.5% of full scale

    Measured value (air-side)

    6

    Power meter

    0–5 kW

    ±0.5% of full scale

    Measured value (refrigerant-side)

    7

    Mass flow meter

    Coriolis

    0–600 kg h–1

    ±0.35% of flow rate

    Measured value (refrigerant-side)

    8

    Refrigerant-side capacity

    ±3.15%

    Calculated value

    9

    Refrigerant-side COPh

    ±3.16%

    Calculated value

    10

    Air-side capacity

    ±6.61%

    Calculated value

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