Ijmet 10 01_178

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International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 01, January 2019, pp. 1804-1813, Article ID: IJMET_10_01_178
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=01
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication Scopus Indexed
CHARACTERISTICS STUDY OF TWO-STAGE
CASCADE REFRIGERATION SYSTEM DESIGN
FOR HOUSEHOLD AIR BLAST FREEZING
Darwin R.B Syaka, I Wayan Sugita and Muhammad Bijaksana
Department Mechanical and Vocational Education State University of Jakarta,
Gedung B Kampus Rawamangun Jl. Rawamangun Muka, Jakarta, Indonesia, 13220
ABSTRAK
The major problem of archipelago communities is the storage of seafood that depends
on a particular season. In order for seafood to be preserved for long periods of time then,
it should be frozen using air blast freezing. However, the existing air blast freezing is still
on an industrial scale. Therefore, the aim of this study is simulation of the two-stage
cascade refrigeration system model, validation and evaluation of the model with
experiment data. This research was preceded by a design for the two stage cascade
refrigeration system R22/R32 followed by experiment to obtain operational parameters
which will then be validated and evaluated of the components of this cascade refrigeration
system. The results of this research are design, operational and analysis methods to
determine parameters and specifications of air blast freezing components including:
pressure of system, cooling temperature, compressor power required, cooling load and
evaluation required for its performance to be better
Keywords: Air Blast Freezing, Cascade Refrigeration System, Design, Evaluation
Cite this Article: Darwin R.B Syaka, I Wayan Sugita and Muhammad Bijaksana,
Characteristics Study of Two-Stage Cascade Refrigeration System Design for Household
Air Blast Freezing, International Journal of Mechanical Engineering and Technology,
10(01), 2019, pp.1804–1813
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&Type=01
1. INTRODUCTION
To improve the economy of the archipelago communities has various problems, such as: capital,
unstable productivity, and various other things. And the most specific thing that usually becomes
the main problem is the storage of marine products that are still dependent on those that exist in
certain seasons. The main results of the archipelago communities are generally fish-based, which
is known, that the fish is easily damaged (rot), and only able to survive about 8 hours after the
arrest. The causes of fish quickly decompose, among others, due to microorganisms, such as
bacteria and fungi[1]. Commonly used storage / preservation methods are basically divided into
4 groups, i.e. 1) using physical factors, 2) preservatives, 3) utilizing physical factors and

preservatives, and 4) fermentation. But for further processing, fish preservation should be done
without changing the texture / shape, taste, and smell of fish. So the best process is to take
advantage of physical factors, and physical factors that mean using low temperatures because the
advantage of using low temperatures will make the material in durable does not change the texture
/ shape, taste, and smell[1].
Commonly used low temperature preservation methods are freezing, air blast freezing or
cryogenic. Comparative study of the 3 methods was performed by M. Bueno, et al. [2]states that
after being stored for 10 months, the method of air blast freezing has the quality of the meat
closest to fresh meat. Similar research conducted by E. Muela, et al. [3] also supports the result
that the method of preservation with air blast freezing at the final temperature of pruduk -18˚C
has the meat quality closest to fresh meat after being stored for 1, 3 and 6 months. This occurs
because the method of fast freezing (blast freezing) offers a new technique for disrupting
microbial cells[4] and with this method the recovery is relatively higher than that obtained by
other methods[5]. As for the marine products should be cooled to the final temperature of -
15˚C[6]. Although the results of the preservation study on the fillet quality of catfish species
with cryogenic method were better than the air blast freezing method but the quality did not differ
significantly[7] but, compared with the 3 preservation methods at other low temperatures,
cryogenic method the highest investment and operational costs[8], therefore the method of air
blast freezing is a preferred method of preserving marine products suitable for archipelago
communities.
Air blast freezing is a cooling technique by utilizing air to keep the temperature inside the
cooling room so that the inside temperature of the cooling room remains stable and there is no
temperature rise in the cooling room[9]. Air blast freezing has flexibility because the air on the
fan can overcome various forms of irregular product and various sizes besides that exhaled air
causes uniform temperature in the cabin room so that cooling can take place evenly. Freezing
with air blast freezing depends on the air velocity and the preparation of the rack so that
circulation can be well circulated then the temperature will quickly cool to produce the optimum
temperature for cooling the product. The advantages of the air blast freezing method are the
flexibility and low capital cost[10] however, the existing blast freezer water cooler in the market
is now still in industrial scale, making it expensive and large in size, therefore air blast freezing
is not suitable for remote archipelago communities that has not too much production.
The capacity of air blast freezing suitable for archipelago communities is on the household
scale. When designing and creating a home-scale air blast freezer is required caution, since failure
in design will result in uneven product freezing[10]. Studies related to the design of today's air
blast freezing focus on the cooling air distribution characteristics. Study of cold air distribution
characteristics performed by Justo et al.[11], stating that using a Computational Fluid Dynamic
(CFD) simulation can improve cooling room design for better cold air distribution optimize fan
power so as to reduce total energy consumption by 12%. A special study of the characteristic
design of cooling air distribution in the freezing process of fish products with industrial air blast
freezing has been carried out by Walnuma et al. [12], using Modelica simulations suggests that
in general this model can be a useful tool for visualization of austerity measures energy. However,
studies on simulation models of air blast freezing refrigeration systems on a household scale are
still difficult to find.
system, so it is proposed to use a two-stage cascade refrigerating system to overcome this
[13]. In the two-stage cascade refrigeration system, the choice of refrigerant pairs in high-
temperature circuits (HTC) and low-temperature circuits (LTC) determines the performance of
the refrigeration system, but kasi study only in simulation models, there is no validation and
evaluation with experimental data[14]. The study of the two-stage cascade refrigeration system
simulation model design and validation of the model with testing is still rarely encountered.

Characteristics Study of Two-Stage Cascade Refrigeration System Design for Household Air Blast
Freezing
Based on what has been described above, the research proposed will concentrate on the design
of the two-stage cascade refrigeration system, validate and evaluate the model with the
experimental data. The main target of this research is to find for design parameters and operation
of household air blast freezing in order to improve the economic resilience of archipelago
communities.
2. METHOD
This research is preceded by design for refrigeration system followed by testing to obtain
operational parameters which further validation and analysis of the design and operational
parameters of this air blast freezer refrigeration system. The design of the two-stage cascade
refrigeration system aims to obtain the appropriate temperature and pressure. The initial design
of the cooling system aims to obtain the appropriate temperature and pressure. This simulation
uses the REFPROP 8 software[15] to determine the thermodynamic property that is needed and
by looking at some of the state points shown in Fig. 1.
Figure.1. P-h diagram and a simple scheme of a two-stage cascade refrigeration system
Balance equations are applied to find the mass flow rate of each cycle, the work input to the
compressor, the heat transfer rates of the condenser and the cascade heat exchanger. The equation
used in the analysis is as follows.
Mass balance
∑∑ =
outin
mm &&
(1)
Energy balance
∑∑ −=−
inout
hmhmWQ .. &&&&
(2)
Specific equations for each system’s components are summarized in table 1.

Table.1. Balance equations for each system component
Component mass energy
High-temperature circuit
Compressor 56 mm && = )( 565 hhmW sH −= &&
Condenser 67 mm && = )( 677 hhmQC −= &&
Expansion device 78 mm && = 78 hh =
Cascade condenser 2385 , mmmm &&&& == )()( 233855 hhmhhmQcas −=−= &&&
Compressor 12 mm && = )( 121 hhmW sL −= &&
Expansion device 34 mm && = 34 hh =
evaporator 41 mm && = )( 411 hhmQE −= &&
The system’s Coefficient of Performance (COP) has been calculated by the following
equation:
LH
E
WW
Q
COP
&&
&
+
=
(3)
Furthermore, the results of the analysis of temperature, pressure and refrigeration capacity
obtained were used as input data to calculate the diameter and length of capillary pipes using
DanCap software[16].
The cascade refrigeration cooling system test equipment consists of two refrigeration circuits,
namely high-temperature circuit (HTC) which will be filled with R22 refrigerant and low-
temperature circuit (LTC) which will be filled with R32 refrigerant. Testing is done by measuring
the temperature out from compressors, condensers, expansion valves, cascade heat exchanger and
evaporators, as well as pressure on high-pressure pipes and low-pressure pipes on before and after
compressors on both HTC and LTC. Temperature measurements are carried out every 1 minute
by the Arduino Uno microcontroller with a digital DS18B20 waterproof thermometer sensor.
Pressure measurement is carried out by analog pressure gauge. The voltage and current needed
by the compressor are measured using digital clamp meter where the results of measurements of
voltage and current are used to calculate the power absorbed by the compressor. The air velocity
circulating in the cooling chamber is measured using a digital anemometer. Data retrieval is done
up to a steady cooling system (steady state) which takes about 180 minutes.
3. RESULT AND DISCUSSION
3.1. DESIGN
The difference between the ambient temperature and the target temperature of -40°C causes a
high compression ratio and high energy requirements so that the compressor's performance is not
stable. Therefore, the use of a two-stage cascade refrigeration system is expected to obtain a stable
cooling system with small energy requirements. The reasons are using R22 and R32 refrigerants
because the two refrigerants are easily found in the market. R22 and R32 each have a boiling
point of -40.8°C and -53.15°C, so that R22 is used as a refrigerant on HTC and R32 for LTC.
The assumptions taken when designing this two-level cascade refrigeration system include:
1. HTC condensers are cooled by air using the temperature of the average outside air in
Indonesia based on SNI standards, namely 34°C dry bulb and 28°C wet bulb so that
40°C temperature condenser and 35°C subcooling are taken.

Freezing
2. Evaporating temperature HTC 0°C and superheating 15°C
3. Temperature difference in the 5°C cascade heat exchanger
4. Evaporating temperature LTC -40°C and superheating -5°C.
5. Cooling capacity is 0.5 kW.
6. Adiabatic compression with isentropic 0.75 efficiency both in compressors on HTC
and LTC.
7. Negligible pressure and heat losses/gains in the pipe networks or system components.
8. Isenthalpic expansion across expansion valves.
9. Negligible changes in kinetic and potential energy
All thermo physical property refrigerants are obtained from REFPROP 8 software [15].
Thermodynamic state points of the cascade refrigeration system are presented in table 2.
Table.2. Calculation of thermodynamic state points of cascade system using REFPROP 8
Evaporator outlet Compressor outlet Condenser outlet Exspansion device outlet
P5 = f (Tcas,E, x=1) P6=P7 P7=f(TC, x=0) P8=P5
T5= Tcas,E T6=f(P6, S5) T7=TC T8= Tcas,E
h5 = f (T5, P5) h6s = f (P6, S5) h7= f (T7, P7) h8=h7
S5 = f (T5, P5) h6 = (h6s – h5)/ηisent+ h5 S7= f (T7, P7) S8= f (P5, h8)
Low-temperature circuit
P1 = f (TE, x=1) P2=P3 P3=f(Tcas,C, x=0) P4=P4
T1= TE T2=f(P6, S1) T3= T5 – DT=Tcas,C T4= TE
h1 = f (T1, P1) h2s = f (P2, S1) h3= f (T3, P3) h4=h3
S1 = f (T1, P1) h2 = (h2s – h1)/ηisent+ h1 S3= f (T3, P3) S4= f (P1, h4)
The REFPROP 8 software is used to determine the thermodynamic property and get the state
points as shown in Fig. 2.

Figure.2. P-h diagram design state points of the two-stage cascade refrigeration cycle
Table.3. the results of calculating the two-stage cascade refrigeration system design
(kW) (kW) (kW) (kg/s)
High-temperature circuit 0.691 0.161 0.853 0.003996966
High-temperature circuit 0.5 0.191 0.691 0.00154335
Furthermore, based on The results of calculating the two-stage cascade refrigeration system
design model in Table 3, DanCap software is used to obtain the length and diameter of the
capillary pipe which functions as an expansion tool both in high temperature circuits and low
temperature circuits.
3.2. EXPERIMENT
Experiment results of the cascade refrigeration system performance and comparison of its
performance with the measured design are based on the coefficient of performance (COP) as
shown in Fig. 3. It can be seen that the COP value of the test result is 1.018, it is lower than the
design which is 1.418, this is because the experiment refrigeration capacity more small than the
estimated refrigeration capacity in the refrigeration system design.

Freezing
Figure.3. Performance comparisons of design and experiments
The refrigeration capacity of experiment smaller than design because the refrigeration cycle
of the R32 refrigerant in LTC does not reach the sub cooling phase when entering the expansion
valve. This can be seen from the actual LTC refrigeration cascade cycle in the ph diagram as
shown in Fig. 4. No achievement of sub cooling phase in condensing LTC is not because HTC
are unable to cool condenser LTC but rather due to ineffective exchange process heat in a cascade
heat exchanger. The effectiveness of the cascade heat exchanger is only 0.63, which means that
only 63% of the heat at HTC can be absorbed by LTC, as shown in Fig. 5.
Figure.4. P-h diagram experiment state points of the two-stage cascade refrigeration cycle
The value of the effectiveness of the heat exchanger is influenced by the temperature in and
out of the fluid in the heat exchanger. Fig. 5 shows a comparison of the inlet and outlet
temperature of the cascade heat exchanger as time increases. To get a high effectiveness value,
the hot fluid exit temperature must be close to the cooling fluid inlet temperature. In Fig. 5, it can
be seen that there is a temperature difference of ±7°C between the exit temperature of R32 (T3)

refrigerant and the temperature entry of refrigerant R22 (T8) in the cascade heat exchanger; this
indicates that the heat exchanger used is less able to exchanger heat effectively.
Figure.5. Cascade heat exchanger temperatures
In Fig. 6 shows a comparison of the temperature of the evaporator and the temperature of the
cooling room along with increasing time. A very significant decrease in temperature at the initial
60 minutes after ignition and in the last 60 minutes the test temperature starts to stabilize. In Fig.
5, it can be seen that there is a difference in temperature ±10°C between the evaporator and
cooling room, this indicates that the evaporator used is less able to absorb heat from the cabin
effectively. However, the target coolant temperature around -30°C has been reached
Figure.6. Temperatures of evaporator and cooling room
Measurement the airflow velocity occurring in the evaporator is only 2.65 m/s. this means
still below the required airflow velocity for air blast freezing of at around 4 m/s [10]. This is what
makes the temperature difference between evaporator and air-cooling room still quite large

Freezing
4. CONCLUSIONS
According to the results of this research, some conclusions can be drawn as follows:
• The design of the two-stage cascade refrigeration system R22 / R32 can be supported
by using Refprop 8 and DanCap software.
• The experiment results obtained are obtained the COP value 1.018 at the temperature
evaporator -40 ° C.
• Based on the analysis of the performance evaluation of the actual two-stage cascade
refrigeration system is lower than the design due to the ineffective heat exchange
process in the cascade heat exchanger.
ACKNOWLEDGMENTS
This research was support by Hibah Penelitian Dasar Unggulan Perguruan Tinggi Tahun
Anggaran 2018, Director General of Higher Education, Minister of Research, Technology and
Higher Education.
NOMENCLATURE
COP [-] Coefficient of performance
DT [o
C] Temperature difference in the cascade-condenser
h [kJ/kg] Specific enthalpy
hs [kJ/kg] Specific enthalpy calculated at suction entropy
m& [kg/s] Mass flow rate
P [bar] Pressure
Q& [kW] Heat transfer rate
S [kJ/kg.K] Specific entropy
T [o
C] Temperature
W& [kW] Work
x [-] Quality
Special characters
η [-] Efficiency
Subscripts
cas Cascade
E Evaporator
C Condenser
H High-Temperature circuit
isent Isentropic
L Low-Temperature circuit
s Isentropic
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