Refrigeration Cycle - Pre-Lab PDF
Refrigeration Cycle - Pre-Lab PDF
Refrigeration Cycle - Pre-Lab PDF
Refrigeration Cycle
Joyjane L. Borres | Ryan Lee G. Ronquillo | John Loui T. Tadia
I. INTRODUCTION
As early as the second century, people had already known the cooling effect of the
evaporation of water but not fully understand it. Evaporation was used in ancient Egypt to chill
jars of water and was also employed in ancient India to make ice. This led to the first attempts
to produce refrigeration mechanically. Refrigeration machines appeared in the 1850s and were
classified according to the type of refrigerants. Nowadays, refrigeration is used in the industry
for cooling and freezing products, condensing vapors, maintaining environmental conditions,
and for cold storage, among many others. (Dincer, 2017).
Refrigeration is basically in reverse effect with the heat pump. It is defined as the
process of extracting heat from a lower-temperature heat source, substance, or cooling medium
and transferring it to a higher-temperature heat sink, atmospheric air or surface water (Wang,
2000). The absorption of heat is usually accomplished by evaporation of a liquid in a steady
state condition. The vapor formed is then returned to liquid state either by compression-
condensation or absorption by liquid at low volatility. This gives us two practical refrigeration
cycle – vapor compression cycle and absorption cycle (Smith et al., 2001).
In the vapor compression cycle, four major thermal processes take place as shown in
Figure 1a. For better understanding and analysis, the cycle can be shown in temperature-
entropy(T-s) and pressure-enthalpy (ln P-h) diagrams in Figure 1b and Figure 1c, respectively.
For this experiment using TCRC/TCRB refrigeration unit, the following equations are
given for the calculations of the obtained results.
Evaporator:
Heat Transfer in the Evaporator: 𝑄𝐸 = 𝑚̇𝑒 𝐶𝑝 (𝑇1 − 𝑇2 ) (Equation 6.1)
Heat Transfer to the surroundings: 𝑄′𝐸 = 0.8(𝑇𝑎 − 𝑇𝑒 ) (Equation 6.2)
Cooling Total Effect: 𝑄′′𝐸 = 𝑄′𝐸 + 𝑄𝐸 (Equation 6.3)
Condenser:
Heat Transfer in the Condenser: 𝑄𝑐 = 𝑚̇𝑐 𝐶𝑝 (𝑇4 − 𝑇3 ) (Equation 7.1)
Heat Transfer to the surroundings: 𝑄′𝑐 = 0.8(𝑇𝑎 − 𝑇𝑐 ) (Equation 7.2)
Total Heat Transfer: 𝑄′′𝑐 = 𝑄′𝑐 + 𝑄𝑐 (Equation 7.3)
Volumetric efficiency
𝑀𝑎𝑠𝑠 𝑓𝑙𝑜𝑤 𝑜𝑓 𝑡ℎ𝑒 𝑐𝑜𝑜𝑙𝑎𝑛𝑡 (𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓𝑐𝑜𝑜𝑙𝑎𝑛𝑡 𝑎𝑡 𝑡ℎ𝑒 𝑖𝑛𝑙𝑒𝑡)
𝑛= (Equation 8)
𝑉𝑜𝑙𝑢𝑚𝑒 𝑠𝑤𝑒𝑝𝑡 𝑏𝑦 𝑡ℎ𝑒 𝑐𝑜𝑚𝑝𝑟𝑒𝑠𝑠𝑜𝑟
Refrigerant is the primary working fluid used in heat exchange in the refrigeration
system. It can be either a single chemical compound or a mixture of chemical compounds
(Wang, 2000). Heat transfer depends on the refrigerant. Different refrigerant will have different
enthalpy values which also depends on the temperatures and pressures of cold and warm
regions (Yeh, n.d.). For this experiment, SES-36 coolant and water are compared. SES-36
coolant is an azeotropic mixture which is at liquid form at room temperature, is chemically
stable with excellent dielectric properties and material compatibility which can be applied to
heat pipes, high temperature heat pumps, and direct contact cooling (Edibon, 2016).
II. OBJECTIVES
General Objective:
1) To conduct and design an experiment on a refrigeration unit.
Specific Objectives:
1) To demonstrate the vapor-compression cycle or heat pump cycle.
2) To determine the relationship between the pressure and temperature.
3) To determine the effect of evaporation and condensation temperatures to the cooling
rate and heat transfer at the condenser.
4) To distinguish the effect of pressure ratio.
5) To calculate for the operation coefficients of the system.
6) To calculate or to estimate for the value of global heat transfer coefficient between the
SES-36 coolant and water.
IV. METHODOLOGY
This experiment will only use a compression refrigeration unit, along with its
accessories, and tap water as cooling liquid. The figure below shows the refrigeration unit that
will be used in the experiment.
PART 2
Atmospheric pressure: ______
Table 2. Experimental results on part 2
CONDENSER
Test number 1 2 3 4 5 6
Relative pressure: PC (bar)
Absolute pressure: PC (bar)
Coolant temperature ST-6: TC (°C)
Water flow: Q2 (1/min)
Water inlet temperature ST-3: T3 (°C)
Water outlet temperature ST-4: T4
(°C)
EVAPORATOR
Test number 1 2 3 4 5 6
Relative pressure: PE (bar)
Absolute pressure: PE (bar)
Coolant temperature ST-9: TE (°C)
Water flow: Q1 (1/min)
Water inlet temperature ST-1: T1 (°C)
Water outlet temperature ST-2: T2
(°C)
Room temperature ST-11: Ta (°C)
Table 3. Data on heat transfer rate vs condensation temperature
Test number 1 2 3 4 5 6
Coolant temperature in the evaporator
ST-9: TE (°C)
Coolant temperature in the condenser
ST-6: TC (°C)
Heat transfer in the evaporator:
QE (W)
Heat transfer in the condenser:
QC (W)
VI. REFERENCES
Dincer, I. (2017). Refrigeration Systems and Applications (109-142nd ed.). Hoboken, NJ:
John Wiley & Sons.
Smith, J. M., Ness, H. C., & Abbott, M. M. (2001). Introduction to Chemical Engineering
Thermodynamics (6th ed., pp. 294-310). New York City, NY: McGraw-Hill Science
Engineering.
Wang, S. K. (2000). Handbook of Air Conditioning and Refrigeration (2nd ed., pp. 428-432).
New York, NY: McGraw-Hill Education.
Yeh, R. (n.d.). 2.972 How A Compression Refrigeration System Works. Retrieved March 6,
2019, from
http://web.mit.edu/2.972/www/reports/compression_refrigeration_system/compressio
n_refrigeration_system.html