. Level 3 Air Conditioning Inspections for Buildings 8. Condensers Day 2 PRESENTED BY Anthony Balaam aircon@stroma.com

Condensers Condensing Process:- Three main types:- 1. Air Cooled (using ambient air) 2. Water Cooled (using mains, river or cooling tower water) 3. Evaporative Condensers (using ambient air and re-circulated water) This area hear

Condensers Condensing Process:- Superheated refrigerant vapour enters the Condenser. Loses heat to a coolant – (e.g. air/ water). Refrigerant vapour is first cooled to its ‘Saturation temperature’. As it condenses to a liquid at constant temperature, ‘Latent Heat (change of state)’ is released. Once condensation has finished, refrigerant temperature will drop again. This further cooling is known as ‘sub-cooling’ – occurs in the ‘liquid line’. In evaporative condensers the cooling is enhanced by allowing water to evaporate in the air blown over the tubes. This cools the air to its ‘Wet bulb temperature’.

Condensation Air or water From the Compressor To the Expansion Device Condenser Condenser

Coolant Temperature (Air or Water)

Condensers Approach Temperature Difference (A.T.D) For heat transfer from the refrigerant to the coolant, a ‘temperature difference’ must exist – ‘approach temperature difference (ATD)’. The ATD must be large enough to provide the heat flow needed to achieve the required system capacity. For maximum efficiency – ATD should be minimised, as this will reduce the temperature lift of the system. A sensible compromise is required to ensure adequate capacity at reasonable cost and environmental impact. Condenser

Approach Temperature Difference (ATD) Condensers Approach Temperature Difference (ATD) Inlet temperature of the coolant is not usually controllable (air/ water). If possible should be selected to have a lower air temperature as possible. The lower the coolant temperature for a given ATD, the higher the efficiency. Coolant temperature naturally rises as it cools the refrigerant. Temperature rise is dependant upon flow rate and the coolant type. For maximum efficiency this temperature rise should be kept low. In turn this means that the condensing temperature can be kept lower. Higher flow rates will need larger fans/ pumps, hence more electrical energy consumed.

Condensers

Condensers 1. Air Cooled Condensers The refrigerant condenses inside the finned tubes by air, driven by fans. If used in a corrosive atmosphere (near sea or in polluted air) then the fins are made of copper, or the fin block is tinned or coated with PVC. These types are susceptible to blockage by airborne debris – dust, feathers, leaves, packaging, etc. Requires regular cleaning – else air flow reduces – condensing pressure increases. If in a vulnerable location the fin block needs to be protected to prevent damage – but air circulation should not be restricted.

Air Cooled Hot Air Air

Air Cooled Examples

Air Cooled Example of fans, blade type Compressor Refrigerant receiver

Air Cooled Examples

Air Cooled Hot Air Air Example

Air Cooled Examples

Condenser Efficiency Issues Each of the three types of Condensers used in refrigeration, all have associated levels of energy consumption which must be taken into account:- Air-cooled – the ‘fan power’. The larger the surface area of the Condenser, the closer the condensing temperature is to the surface temperature of the cooling medium (air/ water). Results in a lower energy consumption.

Efficiency Condenser Efficiency Issues Heat transfer of all Condenser types is reduced if they are dirty:- Air-cooled Condenser fin blocks should be:- free of debris and in good condition.

Condenser Efficiency Issues Condensing pressure should be allowed to float with the ambient temperature to take advantage of the lower ambient air temperatures over night and during winter. This can cause the pressure ratio to vary significantly, and can cause problems with some types of commonly used expansion valve. This can be avoided by using more sophisticated expansion devices like:- Electronic type Balanced port types Or liquid pressure amplification should be considered.

Comparison Simplest and cheapest – to buy and install. Large surface area/size. Higher running costs. Cooling duties up to 500kW. Condensing temperature 10-20K > ambient dry bulb air temperature.

Reference Material “Heating, Ventilation, Air Conditioning and Refrigeration”, CIBSE Guide B, Chartered Institute of Building Services Engineers, 2005 “Energy Efficiency in Buildings”, CIBSE Guide B, Chartered Institute of Building Services Engineers, 2005 “CIBSE KS13: Refrigeration”, CIBSE Knowledge Series, Chartered Institute of Building Services Engineers, 2008 BSRIA Guide AG 15/2002 –” Illustrated Guide to Mechanical Building Services” Carbon Trust Good Practice Guide GPG280 – “Energy efficient refrigeration technology – the Fundamentals” 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” “BS EN 378: Specification for Refrigeration Systems and Heat Pumps; Part 1: 2000: Basic Requirements, Definitions, Classification and Selection Criteria; Part 2: 2000: Design, Construction, Testing, Marking, and Documentation; Part 3: 2000: Installation Site and Personal Protection; Part 4: 2000: Operation, Maintenance, Repair and Recovery”, London: British Standard Institution, 2000

LEVEL 3 Air Conditioning ENERGY ASSESSORS TRAINING ANY QUESTIONS OR FEEDBACK ON ANY SLIDE Any questions or clarity needed over this topic and slides 21

Contacts:- STROMA Certification Ltd – Contacts Web Links www.stroma.com/certification Contacts:- STROMA Certification Ltd. 4 Pioneer Way, Castleford, WF10 5QU 0845 621 11 11 training@stroma.com

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