Refrigeration Engineering
MEREFENG
Module 5:
Actual Vapor Compression Cycle
Subtopic 1 –
Analysis
Intended Learning Outcome
v Be able to know and understand the Actual Vapor Compression Cycle
An ammonia compression plant is to be Leaving evaporator -10 C
designed for a capacity of 50 TR. The Entering compressor -5 C
system operates with a condensing Leaving compressor 95 C
temperature of 40 C and an evaporating Entering condenser 85 C
temperature of -20 C. The other data are Leaving condenser 33 C
shown on the table. A twin cylinder,
Entering expansion valve 36 C
double-acting compressor is to be used.
The heat absorbed by jacket water is Wiredrawing, suction 20 kPa
30% of the indicated work of the Wiredrawing, discharge 40 kPa
compressor. Determine (a) the bore and Compressor speed 400 rpm
stroke, (b) the brake work, (c) the heat Mechanical efficiency 80%
loss or gained between compressor and Volumetric efficiency 77%
condenser, and (d) the heat rejected Stroke-to-bore ratio 1.3
from the condenser.
A simple ammonia compression system has a compressor with a piston
displacement of 1.76 m3/min, a condenser pressure of 1557 kPa and an
evaporator pressure of 227 kPa. The liquid is subcooled to 35 C and the
vapor leaving the evaporator and entering the compressor is -6 C. The
temperature of the vapor leaving the compressor is 90 C. The heat
rejected from the ammonia to the compressor jacket is 5070 kJ/h. The
volumetric efficiency of the compressor is 80%. Determine (a) machine
capacity in tons, (b) IHP of the compressor, and (c) COP of the machine
based on indicated work.
REFERENCES:
• Cengel, Yunus A. (2015). “Thermodynamics: An
Engineering Approach, 8th ed.” Singapore : McGraw-Hill.
• Kleinert, Eric (2015). HVAC and Refrigeration Preventive
Maintenance. United States : McGraw-Hill.
• 3G E Learning (2015). “Air Conditioning and Refrigeration
Technology. United States”: 3G E Learning FZLLC
• Althouse, Andrew D. (2014). “Modern Refrigeration and
Air Conditioning. United States”: The Good Heart Wilcox
Company Inc.
• Stoecker and Jones (1982). “Refrigeration and Air
Conditioning” McGraw-Hill.
Refrigeration Engineering
MEREFENG
PREPARED BY:
RITCHARD Q. DIZON, ME
Full-time Faculty
Mechanical Engineering Department
FEU Institute of Technology
Refrigeration Engineering
MEREFENG
Module 5:
Actual Vapor Compression Cycle
Subtopic 2 –
Application
Intended Learning Outcome
v Be able to understand the Actual Vapor Compression Cycle through
sample problem
Compressor suction 0C
An ammonia compression plant is to Entering condenser 90 C
be designed for a capacity of 30 TR. Leaving condenser 32 C
The cooling water temperature Leaving evaporator -5 C
requires a condenser pressure of Wiredrawing, suction 35 kPa
1400 kPa and a pressure of 291.6 kPa Wiredrawing, discharge 70 kPa
in the brine cooler. The following
temperatures will exist at the points No. of cylinder 2
designated at the table. Determine Piston speed 120 m/min
(a) flow rate of ammonia, (b) the BHP Mechanical efficiency 80%
of the compressor, (c) the heat Adiabatic compression 82%
rejected at the condenser, (d) the efficiency
rpm of the compressor, (e) the COP. Volumetric efficiency 75%
Stroke-to-bore ratio 1.2
(a) 5.685 kg/min; (b) 52.28 hp; (c) 7353.5 kJ/min; (d) 254 rpm; (e) 3.38
REFERENCES:
• Cengel, Yunus A. (2015). “Thermodynamics: An
Engineering Approach, 8th ed.” Singapore : McGraw-Hill.
• Kleinert, Eric (2015). HVAC and Refrigeration Preventive
Maintenance. United States : McGraw-Hill.
• 3G E Learning (2015). “Air Conditioning and Refrigeration
Technology. United States”: 3G E Learning FZLLC
• Althouse, Andrew D. (2014). “Modern Refrigeration and
Air Conditioning. United States”: The Good Heart Wilcox
Company Inc.
• Stoecker and Jones (1982). “Refrigeration and Air
Conditioning” McGraw-Hill.
Refrigeration Engineering
MEREFENG
PREPARED BY:
RITCHARD Q. DIZON, ME
Full-time Faculty
Mechanical Engineering Department
FEU Institute of Technology
What is Compressor ?
Compressor is a device which is used to increase
the pressure of air from low pressure to high
pressure by using some external energy
7/2/2013 1
FORMULA
CAPACITY OF COMPRESSOR
It is the quantity of air actually delivered by a compressor in m3
per minute.
𝑉1 = 𝑣𝑜𝑙𝑢𝑚𝑒 𝑓𝑙𝑜𝑤 𝑎𝑡 𝑠𝑢𝑐𝑡𝑖𝑜𝑛
𝑚𝑅𝑇1
𝑉1 =
𝑃1
COMPRESSION PROCESS (1 TO 2)
P, V, and T Relations
𝑷𝟏𝑽𝒏𝟏 = 𝑷𝟐 𝑽𝒏𝟐
𝒏−𝟏
𝑻𝟐 𝑷𝟐 𝒏
=
𝑻𝟏 𝑷𝟏
𝒏−𝟏
𝑻𝟐 𝑽𝟏
=
𝑻𝟏 𝑽𝟐
PISTON DISPLACEMENT or Swept Volume
Swept Volume 𝑽𝑫
The volume displaced or
swept by piston when it
moves between top
dead center and bottom
dead center.
PISTON DISPLACEMENT or Swept Volume
Piston Displacement with single cylinder
𝝅𝑫𝟐
𝑽𝑫 = 𝒙𝑳𝒙𝑵
𝟒
Piston Displacement with 2 cylinder
𝝅𝑫𝟐
𝑽𝑫 = 𝒙𝑳𝒙𝑵𝒙𝟐
𝟒
𝑳 = bore
𝑵 = stroke
Compressor capacity or 𝑽𝟏
It is the quantity of air actually delivered by a compressor in m3 per minute.
Compressor 𝑽𝟏 ′ actual gas drawn-in at intake condition
Volumetric efficiency – ratio of the actual gas drawn-in at intake
condition to the displacement volume
𝑽𝟏 ′
𝒆𝒗 =
𝑽𝑫
Volumetric efficiency using clearance
𝟏
𝑷𝟐 𝒏
𝒆𝒗 = 𝟏 + 𝒄 − 𝒄
𝑷𝟏
SAMPLE PROBLEM
EXAMPLE 6
EXAMPLE 7
EXAMPLE 10
COMPRESSOR
Work (Polytropic )
𝒏−𝟏 𝒏−𝟏
𝑷𝟐 𝒏 𝒏𝒎𝑹𝑻 𝑷𝟐 𝒏
𝑾= 𝒏𝑷𝟏𝑽𝟏′
−𝟏 = −𝟏
𝒏−𝟏 𝑷𝟏 𝒏−𝟏 𝑷𝟏
EXAMPLE 1
Refrigeration Engineering
MEREFENG
Module 6:
Multipressure Systems
Subtopic 1 –
Definition
Intended Learning Outcome
v To be able to know and understand Multipressure Systems
Multipressure System – is a refrigeration system that has two or
more low-side pressures.
Low-side Pressure – is the pressure of the refrigerant between the
expansion valve and the intake of the compressor.
Flash tank – an equipment
used to separate the vapor
from the liquid.
Intercooling – its main
purpose is to reduce the work
of compression per kilogram
of vapor. Intercooling in a
refrigeration system can be
accomplished with a water-
cooled heat exchanger or by
using refrigerant.
REFERENCES:
• Cengel, Yunus A. (2015). “Thermodynamics: An
Engineering Approach, 8th ed.” Singapore : McGraw-Hill.
• Kleinert, Eric (2015). HVAC and Refrigeration Preventive
Maintenance. United States : McGraw-Hill.
• 3G E Learning (2015). “Air Conditioning and Refrigeration
Technology. United States”: 3G E Learning FZLLC
• Althouse, Andrew D. (2014). “Modern Refrigeration and
Air Conditioning. United States”: The Good Heart Wilcox
Company Inc.
• Stoecker and Jones (1982). “Refrigeration and Air
Conditioning” McGraw-Hill.
Refrigeration Engineering
MEREFENG
PREPARED BY:
RITCHARD Q. DIZON, ME
Full-time Faculty
Mechanical Engineering Department
FEU Institute of Technology
Refrigeration Engineering
MEREFENG
Module 6:
Multipressure Systems
Subtopic 2 –
Application
Intended Learning Outcome
v To be able to know and understand Multipressure Systems through
Sample Problems with Two (2) Evaporators and One (1) Compressor
and Two (2) Compressors and One (1) Evaporator
Calculate the power required by a system of one compressor serving of
two evaporators. One evaporator carries a load of 35 kW at 10 C and
the other a load of 70 kW at -5 C. A back-pressure valve reduces the
pressure in the 10 C evaporator to that of the -5 C evaporator. The
condensing temperature is 37 C. The refrigerant is ammonia. What is
the COP?
Calculate the power required in an ammonia system which serves a
210-kW evaporator at -20 C. The system uses two-stage compression
with intercooling and removal of flash gas. The condensing
temperature is 32 C.
REFERENCES:
• Cengel, Yunus A. (2015). “Thermodynamics: An
Engineering Approach, 8th ed.” Singapore : McGraw-Hill.
• Kleinert, Eric (2015). HVAC and Refrigeration Preventive
Maintenance. United States : McGraw-Hill.
• 3G E Learning (2015). “Air Conditioning and Refrigeration
Technology. United States”: 3G E Learning FZLLC
• Althouse, Andrew D. (2014). “Modern Refrigeration and
Air Conditioning. United States”: The Good Heart Wilcox
Company Inc.
• Stoecker and Jones (1982). “Refrigeration and Air
Conditioning” McGraw-Hill.
Refrigeration Engineering
MEREFENG
PREPARED BY:
RITCHARD Q. DIZON, ME
Full-time Faculty
Mechanical Engineering Department
FEU Institute of Technology
