This document analyzes the transport properties of hydrofluorocarbon (HFC) refrigerants for air conditioning systems. It presents simulated results of a 1 ton air conditioning condenser using HFC-32 refrigerant under different ambient conditions. Key findings include: - UA-value (overall heat transfer coefficient) increases with ambient temperature up to 40°C but then decreases for higher temperatures due to a reduction in log mean temperature difference. - Refrigerant density decreases as ambient temperature increases for a constant air flow rate through the condenser. - Condenser effectiveness can be improved by increasing the air flow rate through the condenser.

1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME
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ANALYSIS OF TRANSPORT PROPERTIES FOR HYDRO
FLUOROCARBON (HFCS) REFRIGERANT FOR AIR –
CONDITIONING SYSTEM
B.HADYA1
, Dr. P. USHA SRI2
1
Assistant Professor, Mechanical engineering department, U.C.E., Osmania University
2
Associate Professor, .Mechanical engineering department, U.C.E., Osmania University
ABSTRACT
This paper presents the simulated results of an Air-Conditioning Condenser with hydro
fluorocarbon(HFCs) group refrigerant of 1 ‘TR’ capacity with available experimental data of
condensing temperature (Condensing Temperature 54.45°C pressure 14.72 bar) with different
ambient conditions (Ambient air Temperatures) as per Indian scenario. The critical factors which
influences design consideration for optimum performance of Air-Conditioning are, ambient
temperature, Compressor selection, Condenser design, air flow through condenser, selection of
refrigerant and refrigerant properties. The overall heat transfer coefficient (U) W/m2
K and Condenser
surface area (A) m2
influences the size of a condenser, i.e the sizing of condenser is described by
UA-value evaluation. The evaluation should include, Gross heat rejection, ambient temperature,
temperature difference and air flow rate. The ambient temperatures of air (cooling medium) from
25°C to 40°C were chosen and results obtained were shown and compared with different ambient
temperature. For the ambient temperature 25°C the simulated UA-value is 0.149 kW/ K and 40 °C the
UA-Value is 0.487 kW/ K. The refrigerant properties play an important role in refrigeration and air
conditioning, if the condenser with constant air flow rate, the density of the selected refrigerant varies
with ambient temperature, for the ambient Temperature 25 o
C and 40 o
C, the simulated density
obtained were 961 kg/m3
and 893 kg/m3
. From the simulated results for higher ambient temperatures
with constant air flow rate 960 (m3
/h), for selected condensing temperature the condenser
effectiveness reduces due to decrease in the log mean temperature difference (LMTD) value. The
variation of UA-value is depends on the type of condenser, compressor capacity, type of refrigerant
used and other transport properties.
For Air –Conditioning installation the important consideration on condenser design is type of
load i.e latent heat load and sensible heat load in this present analysis only latent heat load is
considered at constant condensing temperature for evaluation.
Keywords: Hydro fluorocarbon (HFCs) Alternate refrigerant, Condensing Temperature, UA-value
and LMTD.
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ISSN 0976 - 6480 (Print)
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Volume 4, Issue 3, April 2013, pp. 163-169
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1.0 INTRODUCTION
The significance of refrigeration and air conditioning is increasing every day, the refrigerant
used in refrigeration system plays very important role in refrigeration system. Refrigerant like
Chloro- fluorocarbon (CFC), Hydro Chloro fluorocarbon (HCFC) has been used for many decades
as a working medium because of their better performance, but due to some environmental impact
there is a need to search for alternate refrigerant like hydro fluorocarbon(HFCs), Hydrocarbon(HCs)
have emerged as zero ozone potential depletion and low global warming potential with favorable
performance[1-3].In refrigeration Cycle heat is received at low temperature and rejected at high
temperature, while a net work is done on the fluid (refrigerant).The practical refrigeration cycle is
composed of flow processes, each process being carried out in a separate component. Figure 1 shows
the simple vapour compression refrigeration cycle, the main components of refrigerating system are
Compressor, condenser expanding Device and evaporator the function of the compressor is to
compresses the vapour refrigerant to condenser, condenser is located at high pressure side and its
function is to remove heat from hot vapour refrigerant discharged from the compressor, the function
of the expansion valve is to reduce the pressure. Evaporator is an important device used in low
pressure side of refrigeration system the function of evaporator is to absorb heat from the medium
which is to be cooled by means of refrigerant [3-7].
2.0 LITERATURE STUDY
Condensers are heat exchangers designed to remove the heat absorbed by the refrigerant in
the evaporator and heat of compression added by the compressor. This is achieved by transferring
heat from the refrigerant vapour discharged by the compressor to some external cooling medium,
usually water or air. As result of vapour refrigerant condenses back to the liquid at constant pressure.
Thus the function of a condenser is to get rid of the heat absorbed previously and reliquify the
refrigerant [8-9].In the condenser the pressure is maintains constant, but the temperature is constant
only during the removal of latent heat from the refrigerant i.e. only in the condensing portion.
2.1Classification of Condensers
Condensers are classified as Air cooled condenser, Water cooled condenser and Evaporative
condenser.
2.1.1 Air Cooled condenser
Air cooled condensers were initially used for small refrigerating systems, but now they are
designed in large sizes with capacity of above 100kW.Air cooled refrigerators are widely used for
domestic refrigerators, freezers, water coolers and room air- conditioners.
Air cooled condenser is one in which the removal of heat is done by air which passes through
the finned tubes (copper or steel) with the size of 6 mm 18 mm outside diameter, depending upon the
size of condenser. Generally copper tubes are used because of its excellent thermal conductivity and
heat transfer rate. Condenser absorbs heat from the vapour refrigerant and condenses it in to liquid.
This liquid refrigerant flows out at the bottom of the condenser to expansion device. The main

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advantages of air cooled condensers are simplicity in design, high flexibility, low installation and
maintenance cost and negligible corrosion effect [10-12]
However, their use is restricted to small capacities because of low heat transfer and uneven
distribution of air on condenser surface. For the increase in ambient temperature causes reduction in
the capacity of the condenser. The air cooled condensers requires a large quantity of air. They are
further classified as: Natural draught type and Forced draught type the force draught type further sub
divided as Chassis mounted type and Remote type.
Natural draught condensers are used in small capacity plants such as domestic refrigerators.
Refrigerant vapour enters at the cooling air rises vertically over the condenser surface. The
sufficiently large enough to ensure that the condensation is complete, and liquid refrigerant is sub
cooled before it enters the expansion valve.
In forced draught condenser, a fan or blower provides a steady flow of air for removal of heat
from the refrigerant that flows through the copper tubes. The surface area of the tubes is extended by
providing aluminum fins fan is directly driven by motor or belt driven. Force draught condensers are
used for large refrigerators, food freezers, water coolers and air conditioners. Force draught
condensers are sub-divided into chassis mounted and remote type. In chassis mounted type
compressor and condenser s are mounted on the common chassis as a single unit (Condensing Unit).
Its size is small and, and the capacity is limited up to 3 tons. . In remote type, the condenser is located
away from the compressor. It is usually located on the roof or windows. This type of condensers is
used for fairly large capacity refrigerant system.
3.0 THEORETICAL ANALYSIS:
Figure 2. Temperature Distribution in a Condenser
Figure 2 shows the temperature distribution in condenser with liquid sub cooling and
desuperheating, the refrigeration effect and the heat rejection rate of the system will vary depending
on the actual balance of evaporator, compressor and condenser. Once the compressor and evaporator
selected to perform the required cooling, it is essential that condenser be selected on the basis of the
capability of these components. Thus the selection is made on the heat gain, but rather on the actual
load on the condenser.
Since the heat transfer through the condenser is by conduction, condenser capacity is function
of fundamental heat transfer equation.
3.1 Theoretical calculations for Condenser and ambient air heat transfer rate
Qc = U .A. (LMTD) (1)
Where, Qc = Condenser capacity in kW
U = Overall Heat Transfer Coefficient W/m2
K
A = Effective Surface area m2
LMTD = the log mean temperature difference between the condensing refrigerant
and condensing medium i.e ambient air Temperature °C

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From above equation UA-value and LMTD variation can be determined by changing ambient air
flow rate and air inlet conditions (Temperature inlet)
By Energy balance heat gained by cooling medium
QC = m* Cp* (TOUT, SEC- TIN, SEC) (2)
Where,
QC = Heat Transfer rate (3.5k W)
m =Mass flow rate of air (0.32kg/sec.)
Cp =Specific heat of air (1005 J/Kg K)
TOUT, SEC= Air outlet temperature (K) which is to determine
TIN, SEC = Air inlet temperature (298 K)
4.0. SIMULATION ANALYSIS:
For simulation, REFPROP version 6.01 (REFPROP is an acronym for Refrigerant
Properties) used for finding out the properties of Refrigerant 32 which gives the most accurate pure
fluid property for simulation, developed by the National Institute of Standards and Technology
(NIST) provides the thermodynamic and transport properties of refrigerants REFPROP also provides
high accuracy data for pure refrigerants and refrigerant mixtures, for the simulation the density of the
refrigerant 32 for the condenser were evaluated with ambient temperatures.
Cool Pack (version 1.49) is a collection of simulation programs used for designing,
dimensioning, analyzing and optimizing the refrigeration system, it consist of three main group
Refrigeration Utility ,EES Cool Tool, Dynamic analysis Tool. EES provides high accuracy property
data for pure refrigerant and refrigerant mixtures and used to analyses Cycle performance, System
Dimensioning, Operation analysis, System Simulation and Comparison of Refrigerants.The Programs
in cool pack covers following simulation purpose:
Calculation of Refrigeration Properties (Property plots, thermodynamic and Thermo-physical
data, Refrigerant Comparisons
• Cycle Analysis –Compression of single Stage and Multi Stage.
• System dimensioning-Calculation of component sizes from general configuration criteria
• System Simulation-Calculation Operating conditions in a system with known components with
their operating parameters.
• Evaluation of Operation-Evaluation of the system Coefficient of Performance with less power
consumption
4.1. Simulation for R32 at condensing temperature of 54.45°C, inlet air temp 25°C and air flow
rate is 960 m3
/ h.
Figure 3. Simulation of air ambient temperature at 25°C

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4.2 Simulation for R32 at condensing temperature of 54.45°C, inlet air temp. 40°C and air flow
rate is 960 m3
/ h.
Figure 4. Simulation of air ambient temperature at42°C
Figure 3 &4 shows that the Simulation of Condensing Temperature of refrigerant 32 at 54.45°
C for the model used for testing ambient conditions according to ASHRAE, ISO and other standard
data for higher ambient conditions. In this model, the testing situation is specified by setting the input
parameters like temperature Tc , TIN SEC , Ambient air flow rate VSEC(m3
/h) and Capacity.
5.0. RESULTS AND DISCUSSION
Table 1: Shows that variation of UA-value with LMTD
Table 1 shows the variation of UA-value with log mean temperature difference and condenser
density variation for the selected refrigerant for conditioning temperature 54.45°C of selected
refrigerant R32 with different ambient temperaturs from 25°C to 40 °C. From the table 1, it is
observed that overall heat transfer coefficient is a function of ambient air flow rate and temperature
difference.
Air Cooled
Condenser
Temp. of
cooling medium
(Air)
UA-Value
(kW/K)
LMTD
(K)
Density
(kg/ m3
)
Refrigerant
R32
Condenser
temp.(Tc)
54.45°C
25°C 0.149 23.52 961
30°C
0.191 18.28 939.6
35°C
0.271 12.94 917
40°C
0.487 7.18 893

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Figure.5. Variation UA-value (kW/K) with Ambient Temperature
Figure 6. The variation of density for the Refrigerant 32 with ambient air temperature
Figure 7. The variation of Condensing Temperature with LMTD.
Figure 5 shows the simulated results of overall heat transfer coefficient with ambient
temperature UA-Value increases with ambient temperature for constant mass flow rate of air. For
further higher ambient temperature the UA-Value reduces. Figure 6 show that the density for the
selected refrigerant varies with ambient temperature for the condenser of constant air flow rate .Figure
7 shows the Log mean temperature difference (LMTD) variation with different ambient temperatures.
Performance of selected condenser is depends on Overall heat transfer coefficient UA-value
increases with ambient temperature , for higher ambient temperature with same mass flow rate UA-
value reduces , if air circulation is increased effectiveness of condenser may be increased.

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6.0 CONCLUSIONS
Simulation results shows that for the condenser of capacity 1 “TR” Air-Conditioning
system, the Overall Heat transfer coefficient is very effective up to ambient temperature 40o
C with air
flow rate of 960 m3
/h. if the air flow rate is constant for ambient temperature 45 o
C the condenser
performance is decreases because of the decrease in the LMTD, hence the system performance will
decrease. The density for the selected refrigerant varies with ambient temperature for the condenser of
constant air flow rate at ambient Temperature 25 o
C the simulated density obtained is 961 kg/m3
, for
temperature 40 o
C density 893 kg/m3
. The effectiveness of the condenser can be increased by
increasing air flow rate. The variation of UA-value is depends on the type of condenser, compressor
capacity, type of refrigerant used and other transport properties. , From the simulation results it is
observed that overall heat transfer coefficient is a function of ambient air flow rate and temperature
difference.
For Air –Conditioning installation the important consideration on condenser design is
type of load i.e latent heat load and sensible heat load in this present analysis only latent heat load is
considered at constant condensing temperature for evaluation.
Acknowledgement
This part of research work has been carried out under O.U/D.S.T-PURSE Programme,
Scheme no A-38. Under the esteem Guide of Dr.P.Usha Sri, Associate Professor, Department of
Mechanical Engineering, University College of Engineering (A), Osmania University- Hyderabad.
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