. Level 3 Air Conditioning Inspections for Buildings 5. Mechanical Refrigeration (Day 2) PRESENTED BY Anthony Balaam

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Basic Rules of Physics 1)Heat flows naturally from ‘hot zone’ to a ‘cold zone’. 2)Energy (in the form of heat) is required to change a substance from a ‘liquid’ to a ‘gas’ (boiling/ ‘evaporation process’). 3)When this happens the liquid absorbs large amounts of heat. 4)Energy is given out by the substance changing from a ‘gas’ into a ‘liquid’ (liquefying/ ‘condensing process’). 5)The ‘boiling temperature’ and ‘condensing temperature’ change if the ‘pressure’ changes (compression process). Mechanical Refrigeration

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Refrigeration  A refrigeration system transfers heat from a substance to be cooled to another area (usually the outside air).  Most refrigeration systems use the ‘Vapour Compression Cycle’.  Heat is absorbed through a ‘heat exchanger’ as the refrigerant ‘evaporates’.  Heat is rejected through another ‘heat exchanger’ as the refrigerant ‘condenses’.  ‘Absorption’ cooling may be used if there is a lot of ‘free waste heat’. Mechanical Refrigeration

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Refrigeration:-  This is the fluid used by the system.  This boils at a low temperature (usually between -10˚C and - 45˚C) when at low pressure (the saturation pressure, usually between 1 and 5 bar). (dependant on the type of refrigerant being used)  Its boiling or evaporating pressure can be controlled so that it boils at a temperature lower than that of the product to be cooled (Rules 4 and 1). Mechanical Refrigeration

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Refrigeration  The refrigeration system cools air, or liquid – secondary refrigeration – which in turn cools the occupants. Mechanical Refrigeration  The space being cooled provides the energy to evaporate the refrigerant – Rule 2.

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping The ‘Vapour Compression Cycle’ Within the refrigeration cycle:-  1. ‘heat’ is ‘absorbed’ from the medium being cooled (at low temperature);  2. ‘heat’ is ‘rejected’ at a higher temperature, usually ambient temperature;  3. refrigerant is a working fluid within this system. Processes involved are :-  1. Evaporation  2. Compression  3. Condensation  4. Expansion Mechanical Refrigeration

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping The Vapour Compression Cycle Mechanical Refrigeration Principle Components of Vapour Compression Cycle Enthalpy kj/kg Pressure-Enthalpy Chart

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Components of the Refrigeration Cycle Mechanical Refrigeration

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Mechanical Refrigeration 1.SATURATED MIXTURE OF LIQUID/VAPOUR 3.SUBCOOLED LIQUID 2.SUPERHEATED VAPOUR ‘Evaporator’ ‘Compressor’ ‘Condenser’ ‘Expansion Valve’

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Evaporation 1→2  Low pressure liquid refrigerant (1) in the Evaporator.  Absorbs heat energy from its surroundings (air, water, or other process liquids).  liquid undertakes a change of state to a saturated vapour.  At the Evaporator exit (2), the refrigerant is now a vapour and is slightly superheated. Thermodynamics ‘Evaporator’ (1) (2)

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Superheat 2→3  Slightly superheated refrigerant vapour picks up more energy from the ‘ambient air’ around pipework between Evaporator and Compressor.(we are talking about the pipework)  Note- This is ‘Bad’ for ‘efficiency’. Thermodynamics ‘pipework’ (2) (3)

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Compression 3→4  Superheated vapour enters the suction side of the Compressor, where its pressure is raised.  Large increase in ‘temperature’ as compression energy is transferred to the refrigerant purely ‘as heat’.  Further superheat takes place. Thermodynamics (3) (4) ‘Compressor’

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping De-Superheat 4→5  Very hot vapour loses a small amount of heat to ambient air in pipework between the Compressor and the Condenser (again due to the piework).  Note – This is ‘Good’ for ‘efficiency’. Thermodynamics ‘pipework’ (4) (5)

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Condensation 5→6  High pressure superheated vapour flows into the Condenser.  Initial part of the cooling process (5→5a), de-superheats the vapour before it turns back into saturated liquid (5a→6).  Cooling for this process is usually achieved by using ‘ambient air’ or ‘water’ as the heat receiver. Thermodynamics Condenser de-superheats (5) (6) (5a)

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Sub-Cooling 6→7  Further reduction of ‘temperature’ may occur between the Condenser and Expansion Device (pipework within the chiller Unit).  Refrigerant ‘liquid’ is sub- cooled as it enters the Expansion Device.  Note – This is ‘Good’ for ‘efficiency’. Thermodynamics Expansion device sub-cooled Condenser (6) (7)

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Expansion 7→1  High pressure sub-cooled liquid passes through the Expansion Device.  The device gives a reduction in refrigerant pressure, resulting in a reduction in ‘temperature’.  No ‘energy loss’ or ‘gain’ through Expansion Device itself. Thermodynamics Expansion device. (7) (1)

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Flashing between 7 & 1  Outlet of the Expansion Device & the inlet to Evaporator do not lie on the saturated liquid line.  At ‘lower temperatures’ the refrigerant cannot contain as much heat.  This excess heat causes the refrigerant to ‘evaporate’ during ‘expansion’. Thermodynamics (1) (7) Expansion device.

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Evaporation 1→2  Evaporator contains the refrigerant.  Refrigerant ‘boils’ or evaporates at ‘low pressure’.  Refrigerant ‘absorbs heat’ from the surroundings during this process. Hardware Cooling effect of the Evaporator is governed by:-  1, the Temperature difference between ‘medium being cooled’ and the ‘evaporating refrigerant’.  The greater the ‘temperature difference’ the greater the ‘rate of heat transfer’.  2.The ‘size’ and the design’ of the Evaporator is very important. This area hear

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Superheat 2→3  Refrigerant absorbs heat from the ambient air temperature around the suction line between ‘Evaporator’ and the ‘Compressor’.  ‘Superheating’ should be ‘minimised’ by ‘insulation’ to maintain ‘efficiency’. Hardware This area hear

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Compression 3→4  Compressor, compresses the refrigerant vapour from a ‘low pressure’ of the ‘Evaporator’ to the ‘high pressure’ of the ‘Condenser’.  Refrigerant vapour also heats up during this process. Hardware Compressor capacity is affected by:-  1. the Compressor displacement (m 3 /s).  2. the difference between the ‘evaporating’ and ‘condensing temperatures’ (called ‘Temperature lift’).  Pressures of the Evaporator and Condenser are proportional to their respective temperatures.  3. the Superheated suction vapour temperature.  4.the Properties of the refrigerant. This area hear

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping De-Superheat 4→5  High pressure refrigerant vapour flows from the ‘Compressor’ to the ‘Condenser’.  Small amounts of ‘heat energy’ is lost to the ‘ambient air’.  This should be maximised for best efficiency. Hardware This area hear

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Condensation 5→6  Condenser contains the refrigerant which is ‘changing’ from a ‘superheated vapour‘ into a ‘liquid’ at ‘high pressure’.  A lot of heat energy is released during this process, which is rejected to the ‘ambient air’ or ‘cooling water’. Hardware Condenser capacity is affected by:-  1.the ‘Temperature’ of cooling air or water.  2. the Size and design of the Condenser. This area hear

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Sub-Cooling 6→7  The liquid refrigerant flowing between ‘Condenser’ and the ‘Expansion Device’ usually loses heat to the ambient air.  Sub-cooling is beneficial to the system as it ‘increases refrigeration capability/ capacity’ without ‘increasing’ the electrical power input. Hardware This area hear

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Expansion 7→1  ‘Expansion Device’, maintains the ‘pressure drop’ between the ‘Condenser and the ‘Evaporator’.  The refrigerant’s ‘saturation temperature’ also reduces as the pressure drops.  ‘Expansion Device’, is sized to pass the required amount of refrigerant and the minimum likely ‘pressure drop’ across the system. Hardware This area hear

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Reversabilty Mechanical Refrigeration

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping Mechanical Refrigeration

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping “Heating, Ventilation, Air Conditioning and Refrigeration”, CIBSE Guide B, Chartered Institute of Building Services Engineers, 2005 “CIBSE KS13: Refrigeration”, CIBSE Knowledge Series, Chartered Institute of Building Services Engineers, 2008 Carbon Trust Good Practice Guide GPG280 – “Energy efficient refrigeration technology – the Fundamentals” “ASHRAE Handbook: Fundamentals”, American Society of Heating, Refrigeration and Air Conditioning Engineers, 2001 ROGERS and MAYHEW: “Engineering Thermodynamics: Work and Heat Transfer” TROTT, A. R. (2000), “Refrigeration and Air-Conditioning (3rd ed.)” WANG, S. K.: “Handbook Of Air Conditioning And Refrigeration” JONES, W. P.: “Air Conditioning Applications and Design” Reference Material

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping LEVEL 3 Air Conditioning ENERGY ASSESSORS TRAINING ANY QUESTIONS OR FEEDBACK ON ANY SLIDE

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping STROMA Certification Ltd. 4 Pioneer Way, Castleford, WF10 5QU Web Links Contacts:- STROMA Certification Ltd – Contacts

© Stroma Certification 2014 | Version 1.0 Stroma Certification – ABBE Level 3 Air Conditioning course material 2015 House keeping End of this section Test 4. - Mechanical Refrigeration exercise – 32 Questions