This document contains information about a refrigeration and air conditioning (RAC) course, including lesson objectives, recaps of topics like latent and sensible heat, diagrams of vapor compression cycles and phase changes, and diagrams labeling RAC system components. It discusses concepts like superheat, subcooled liquid, where latent and sensible heat occur in RAC systems, and lists components like the compressor, condenser, evaporator, expansion device, and others. The document aims to teach students about heat transfer and vapor compression cycles in RAC systems through definitions, diagrams, and a labeling activity.

1. www.cardiffandvalecollege.ac.uk

2. Class Rules / Rheolau Dosbarth
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3. Lesson Objectives / Amcanion Gwersi
Knowledge of Latent
& Sensible Heat
Apply theoretical
knowledge to
vapour
compression cycle
List RAC system
components
within the vapour
compression cycle
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4. Recap – 18/04/2016
1. What is Superheat?
Superheat is the term given to a vapour above the boiling point ( saturation temperature)
of a substance.
As the substance is above its boiling point, the term superheat can only be applied to
Vapour only.
2. What is Sub-Cooled Liquid?
Sub-cooling is a term given to a liquid that is below its boiling point.
As the liquid is below its boiling point and above freezing point, the substance must
be in its Liquid state only.
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5. Latent Heat - Gwres Cudd
Latent heat causes a change in phase but not in
temperature.
Example:
The temperature remains constant but the substance changes
its nature from solid to liquid or liquid to vapour – Boiling ,
melting or freezing points of a substance.
Where would you find latent heat take place on a RAC System?
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Condenser & Evaporator

6. Sensible Heat - Gwres Synhwyrol
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Sensible Heat causes a change in temperature
but not in phase (state).
Example:
When a substance gains heat its temperature rises but does
not change from a solid to liquid or from a liquid to a vapour.
Where would you find sensible Heat on a RAC system?
Compressor Suction – Compressor Discharge – Condenser Sub cooling

7. Phase Diagram for 1Kg of Water
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100
50
0
-10
Latent Heat
Sensible Heat
Heat
kJ/kg K
Temp °C
Ice + Water
2.1 335 4.2 2260
Solid Liquid Water + Steam
Latent Heat
Sensible Heat
Superheated
Water Vapour

8. RAC Vapour Compression
Cywasgu Anwedd RAC
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High Pressure (warm)
Superheated Vapour
Condenser
Rejecting
Latent
Heat
High Pressure (warm) Sub-
cooled Liquid
Low Pressure (cold)
Superheated Vapour
Evaporator
Absorbing
Latent
Heat
Low Pressure (cold) Liquid / Vapour
Mixture. Saturated 2 Phase Mix

9. System Components
Cydrannau System
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Compressor
Condenser
Evaporator
Expansion
Device
Drier
Sight glass

10. System Components - 2
Cydrannau System - 2
High & Low Pressure
Switch
Suction Line
Accumulator
• Liquid Line Receiver
Liquid Line Solenoid
Valve
Oil Separator
Vibration Eliminator
• Could be used on
discharge or suction
Suction
Drier
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Workshop & Identify the Components

11. Task 1 - Tasg 1
In pairs using the laminated resources, label up
the RAC Vapour Compression System.
*You have a total of 15 minutes for this task*
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12. Feedback
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Compressor
Discharge
High pressure –
superheated vapour
Condenser
High pressure super
heated vapour to High
pressure liquid
After Condenser
High pressure sub-
cooled liquid
TXV to Evaporator
Low pressure
saturated 2 phase
mixture
Evaporator to
Compressor
Low pressure
superheated vapour
High
Pressure
Low
Pressure
Sensible Heat Gain / Loss
Latent Heat Rejection
Sensible Heat Loss
Latent Heat Absorbed
Sensible Heat Gain / Loss

13. Recap of Objectives
Have we achieved the
following objectives?
•Knowledge of Sensible &
Latent Heat
• List RAC System Components
•Apply theoretical knowledge
to RAC vapour compression
cycle.
Any
questions?
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Cwestiynau?