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Optimal Charge Amount for Different Refrigerants in Air-to-Water Heat Pumps

  • Faraz AfshariEmail author
  • Omer Comakli
  • Nesrin Adiguzel
  • Sendogan Karagoz
Research Paper

Abstract

This paper describes an experimental study on the heat pump performance and compressor suction pressure, in order to find out the optimal refrigerant charge amount for different refrigerants. Independent of the choice of refrigerant, environmental and safety problems can be reduced by detecting the optimal amount of refrigerant charge in the heat pumps or refrigeration systems. In this investigation, a laboratory air-to-water heat pump was built to find out the charge effects on the coefficient of performance and heating capacity for three different gases including R22, R134a and R404a. Gas injection was done gradually into the system, and results were obtained and recorded at each stage. It was shown that refrigerant overcharge and undercharge decrease performance of the unit. Although heating capacity increases gradually, compressor work increases with additional charge and there must be an optimum charge amount to obtain the maximum coefficient of performance.

Keywords

Heat pump Refrigerant Charge optimization COP 

List of symbols

COP

Coefficient of performance

GWP

Global warming potential

ODP

Ozone depletion potential

p

Pressure (kPa)

\(\dot{W}\)

Compressor power (W)

T

Temperature (°C)

Cp

Specific heat capacity (J kg−1 K−1)

h

Refrigerant enthalpy (kJ kg−1)

\(\dot{Q}\)

Heat transfer rate (W)

AWHP

Air-to-water heat pump

I

Electric current (A)

U

Voltage (V)

\(\dot{m}\)

Mass flow rate (kg s−1)

k

Thermal conductivity (W m−1 k−1)

g

Gravity (m s−2)

hc

Heat transfer coefficient (w m−1k−1)

D

Condenser diameter (m)

r

Condenser radius (m)

L

Condenser length (m)

B

Coefficient of thermal expansion (k−1)

v

Kinematic viscosity (m2 s−1)

\(\dot{e}\)

Energy loss (W)

Subscripts

a, e

Air passing through evaporator

w, c

Water passing through condenser

evap

Evaporator

comp

Compressor

cond

Condenser

r

Refrigerant

a

Air

w

Water

HP

Heat pump

as

Asbestos

o

Outer

i

Inner

s

Condenser surface

in

Inlet

out

Outlet

T

Total

Notes

Acknowledgments

This project was supported by the Research Project Foundation of the Ataturk University (Project No. BAP-2013/105). The authors gratefully acknowledge the support of this study.

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Copyright information

© Shiraz University 2016

Authors and Affiliations

  • Faraz Afshari
    • 1
    Email author
  • Omer Comakli
    • 1
  • Nesrin Adiguzel
    • 2
  • Sendogan Karagoz
    • 1
  1. 1.Department of Mechanical EngineeringAtatürk UniversityErzurumTurkey
  2. 2.Department of Mechanical EngineeringKafkas UniversityKarsTurkey

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