Perth Refrigeration System Design and Analysis Assignment

This assignment solution analyzes a multistage refrigeration system located in Perth, Australia, addressing the cooling requirements for a room (105kWR at 2°C) and a freezer (200kWR at -18°C). The solution calculates the maximum possible condensing temperatures based on Mycom reciprocating compressors (6WB and 8WA) using refrigerants like R717, R22, R502, R12, and propane, considering their isentropic efficiency and the impact of climate conditions. The document presents calculations and provides recommendations for climate regulation, emphasizing the importance of compressor management, refrigerant selection, and maintenance to ensure consistent cooling performance, especially during periods of higher ambient temperatures. The analysis incorporates Perth's climatic data and suggests maintenance strategies to mitigate potential system failures. The solution also includes references to relevant sources, such as Google Search for Perth climate conditions and the World Meteorological Organization.

REFRIGERATION ASSIGNMENT
DATA AVAILABLE: Location of assessment = Perth metropolitan area, Multistage system
(room cooling capacity = 105kWR at 2 degree centigrade and freezer cooling capacity =
200kWR at -18 degree centigrade), change in temperature when evaporator is flooded = 6
kelvin, reciprocating compressor (Mycom) of 6WB for room and 8WA for the freezer with
isentropic efficiency of 80%, air cooled condenser with negligible sub cooling, closed
expansion valve working at 2 degree centigrade, liquid supplied to low stage expansion valve
at 8 kelvin and short piping runs.
Solution 1: To find maximum possible condensing temperature based on the Mycom
compressors of 6WB AND 8WA rating.
Refrigerant used in the compressors = R717, R22, R502, R12 and propane.
Cooling capacity of compressor in room = 105kWR
Displacement at maximum speed (6WB) = 573 m3/h
Cooling capacity of compressor in freezer = 200kWR
Displacement at maximum speed (8WA) = 374 m3/h
Capacity control steps for both compressor = 100, 66, 33.
Isentropic efficiency of compressor =¿]
As stated in the question, isentropic efficiency of compressor is 80%.
We also have, ∆T = 6K
Liquid flow temperature T3 = 8k
T1 = 275k, T2 = 255k
The maximum possible condensing temperature will be:
For room = 281K, for freezer = 261k

According to the data provided in the question and the datasheet, we can assume that the
maximum condensing temperature cannot exceed the temperature difference of the
evaporator; the compressor work is to compress the evaporator produced air to dense form
with pressure and transfer it to the condenser; where the condenser utilises the refrigerant and
removes excess amount of heat from the air and thus cools the surrounding. The condenser
maximum temperature to cool depends on its limit such as a refrigeration system is built to
withstand a limit of -20 degree Celsius to 25 degree Celsius with proper working in the
atmospheric temperature not more than 50 degree Celsius, then the condensing system works
fine in the provided limit only. If temperature is set to 24 degree Celsius then the condenser
works till the surrounding temperature is achieved as set but if the temperature is set to lower
level the condenser works for long after it achieves the set temperature as it is lower
temperature then the surrounding temperature. Concluding all we can state that the maximum
temperature of a condensing unit depends on the equipment used and the regulation of
temperature with the help of thermostat.
Solution 2: The Perth climate conditions are illustrated in the table below ("Perth climatic
condition - Google Search", 2019):
Month High / Low(°C) Rain
January 30° / 19° 1 day
February 31° / 20° 1 day
March 29° / 18° 1 day
April 25° / 15° 5 days
May 22° / 12° 10 days
June 19° / 11° 14 days
July 18° / 10° 14 days
August 19° / 10° 12 days
September 20° / 11° 10 days
October 22° / 13° 6 days
November 25° / 15° 4 days
December 28° / 17° 1 day

The process used in the documentation are based on the software utilised to gain the correct
climate temperatures around the world synced with temperature measuring device such as
silicon diode, thermocouple, radiation thermometry, bimetallic devices, capillary sensors and
many more. The devices are active all the time and the temperature fluctuations are measured
accurately and precisely for future use and weather forecast. The need to measure the CO2
percentage in the air is also necessary to control the temperature changes effects on the
cooling conditions of the systems. According to the data above, temperature above or equal to
28 degree is on almost 4 days in a year when the cooling could be affected. For that the
systems needed to be properly maintained assuming the same climate conditions would occur
in the next year.
Solution 3: In order to recommend the climate regulation for the fluctuating days the
compressors should be effectively managed a maintained for decreasing the percentage of
failure to provide adequate cooling in the room and the freezer that is to be maintained at 2
degree Celsius and -18 degree Celsius respectively. Since the compressors and the required
room temperatures cannot be altered, there is a need to change the refrigerant, clean the pipes
carrying refrigerants and maintain good quality flow of water over the period of time.

REFERENCES
Perth climatic condition - Google Search. (2019). Retrieved 10 October 2019, from
https://www.google.com/search?client=firefox-b-d&q=perth+climatic+condition
World Metrological Organization. (2012). An analysis of current and emerging capacity gaps
in surface and upper air observations to support climate activities [Ebook] (pp. 1-32).
Geneva. Retrieved from https://www.google.com/url?
sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=2ahUKEwjClY
LoxJHlAhXUQ30KHQagCrkQFjAAegQIARAC&url=https%3A%2F
%2Fwww.wmo.int%2Fpages%2Fprog%2Fwww%2FOSY%2FSOG%2FSoG-
Climate-CCl.doc&usg=AOvVaw1fz6zVE1REMopALlVBrb5i