powerpoint

Unit 204Scientific Principles

Simple mechanical principles and their application in the mechanical

services industry

www.cardiffandvalecollege.ac.uk

Luke Gonzales TMInstR EngTech LCIBSE

Class Rules / Rheolau Dosbarth

Mobile Phones on silent – In Pockets

Appropriate Language

Questions throughout


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


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.


Latent Heat - Gwres CuddLatent 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?


Condenser & Evaporator

Sensible Heat - Gwres Synhwyrol


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

Phase Diagram for 1Kg of Water


100

50

0

-10

Latent Heat

Sensible Heat

Heat kJ/kg KTemp °C

Ice + Water

2.1 335 4.2 2260

Solid Liquid Water + Steam

Latent Heat

Sensible Heat

Superheated Water Vapour

RAC Vapour Compression Cywasgu Anwedd RAC


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

System Components Cydrannau System


Compressor

Condenser

Evaporator

Expansion Device

Drier

Sight glass

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

www.cardiffandvalecollege.ac.ukWorkshop & Identify the Components

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*Ask if you require any assistance


Feedback


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

vapourHigh

PressureLow

Pressure

Sensible Heat Gain / Loss

Latent Heat Rejection

Sensible Heat Loss

Latent Heat Absorbed

Sensible Heat Gain / Loss

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?


Cwestiynau?

powerpoint

Documents