0. Introduction to Refrigeration
STAR PRODUCTS
& SYSTEMS
Introduction to Refrigeration
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1. Saturation Temperature
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2. Introduction A pressure – Enthalpy (P-H) Diagram is a useful device to
2nd Law of Thermodynamics States:
“Heat cannot of itself pass from one body to a hotter body”
Need to do work to compress this refrigerant gas
Refrigeration cycle needs
A Compressor
A Condenser
An Expansion Device
An Evaporator
A pressure – Enthalpy (P-H) Diagram is a useful device to
understand what is happening in the cycle
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3. Simple Refrigeration System
Consist of the following:
- Evaporator (low pressure – Liquid to Vapour)
- Compressor (low to high pressure – Vapour)
- Condenser (high pressure – Vapour to liquid)
- Expansion Device (high to low pressure – Liquid) 2 3
High Pressure Liquid
High
Pressure Vapour
Condenser
Expansion
Device
Compressor
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Evaporator
Low
Pressure Vapour 1 4

4. Thermophysical Properties of Refrigerants
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5. Pressure-Enthalpy Diagram for R717
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6. Points to look for Bar G and Bar A Sensible heat kJ/kg
Latent heat kJ/kg
Saturated liquid line
Saturated vapour line
Vapour quality/dryness fraction
Compression ratio (CR)
Sub cooling
Superheat
Refrigerating effect (RE) kJ/kg
Work done by compressor (WD) kJ/kg
Coefficient of performance (COP)
COP = RE WD
Note: RE x mass flow rate = kJ x kg = kJ = kW
kg s s
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7. Bar (G) ACR News 2005 Contractor of the Year (>£10m turnover)
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8. Refrigeration cycle R717 (Ammonia) R22
Now let’s consider this refrigeration cycle with two very different refrigerants:
R717 (Ammonia)
R22
Evaporating pressure bar(A)
Evaporating temp °C
Condensing pressure bar(A)
Condensing temp °C
Discharge temp °C
Refrigerating effect kJ/kg
Specific volume at suction m³/kg
Refrigerating effect kJ/ m³
Mass flow rate kg/s
0.715
-40.0
13.5
35.0
90.0
1195.0
1.6
746.9
0.418
1.05
183.0
0.23
795.6
2.73
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9. Any Questions ? Questions? Turnover £25m Locations HQ in Glasgow
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