* New York City Chapter Association of Energy Engineers Energy 101 - Air Conditioning September 16, 2014 Presented by Timothy Lynch, PE, CEM, EBCP, LEED AP * Some basic “Rule-of-Thumb” energy calculations * What are the basic AC system components * Understand the vapor compression cycle * Learn about different system/equipment types * * Some slides in this presentation were provided by: * Building Operator Certification, Seattle WA. * a competency-based training and certification program for building operators & * Michael Bobker of the CUNY Building Performance Lab * *  Conduction: direct transfer of heat through materials  Convection: transfer of heat by movement of air  Radiation: surface-to-surface effect  Sensible heat: heat sensed (change in temperature)  Latent heat: heat from change in state * 1 Ton Refrigeration = 12,000 Btus/h or the amount of heat energy needed to melt one ton of ice in one hour * * Coefficient of Performance (COP) = Refrigeration effect / input in btu 1 ton = 12,000 btu 1 kw = 3,410 btu 1# LP steam = 1,000 btu * 1 kw/ton: 12,000/3,410 = COP of 3.5 * 20 #/ton: 12,000/20,000 = COP of 0.6 * Energy Efficiency Ratio (EER) = Btu cooling / input in watts * 1 kw/ton: 12,000 / 1,000 = EER of 12 * .5 kw/ton: 12,000 / 500 = EER of 24 * EER of 6: 12,000/ 2,000, ie – 2 kw/ton * 7 Q (Btuh) = 500 x GPM x TD *“500” = Specific heat of water (1.0 Btu/lb/oF) x Density (8.33 lbs/gal) x 60 minutes/hour Q (Btuh) = 1.08 x CFM x TD *Specific heat of air (0.24 Btu/lb/oF) x Density (0.075 lb/ft3) * x 60 minutes/hour Where TD: temperature difference (or “∆ (delta) T”) usually set equal to 10 oF for cooling or 20 dT (heating) * Cool Generator: Compressor * Heat In: Evaporator * Thermal Expansion * Heat Rejection: Condenser, Cooling Tower * Also, Distribution: Ducts, fans, pumps, coils * * Types of cooling machines * DX * Package units * Through the wall (TTW) * room air conditioners (RAC) * Heat pumps * Air-to-air * Hydronic * Chillers * Air Cooled * Water Cooled * Compressors *Positive Displacement *Reciprocating, open or hermetic *Rotary *Scroll * Usually electric motor * Alternative drives * Engine (natural gas) * Steam Turbine (steam, high pressure) * Gas turbine (stationary jet engine, natural gas) * * * * AC mode *Vapor-compression cycle in reverse *Use for heating *Extract low temperature heat and boost to useful temperature *Environmental sources – solar, ground, ground water *Waste heat Heating * A Simplified Schematic *Shell-and-tube heat exchangers added to condenser and evaporator coils to create a water-cooled chiller. *Circulating pumps for chilled water and condenser water systems * Chiller – showing compressor (top) and two tube bundles (condenser and evaporator) Credit: M Bobker * *Hot Gas By-pass *Unloaders *Multiple compressor staging *Inlet Vanes (centrifugal compressors) *Variable Speed drive control, including variable refrigerant flow When cooling load is light, we can reduce compressor work by lowering the evaporator temperature (chilled water temperature reset). But what happens at the compressor? * Mechanisms *Water-cooled condenser *Air-cooled condenser *Evaporative condenser *Cooling tower Operating Considerations *Condenser temperature reset (improves compressor efficiency) *Condenser Heat Recovery *Water-side Economizer Typical Chilled Water System Schematic *CFC *Chlorine impacts on upper *R11, R12, R502 – out of production atmosphere - Ozone depletion *HCFC *International agreement – *R22, R123 – being phased out Montreal Protocol *HFC *Certification for handling, *R134a especially to prevent venting to atmosphere during service *Chlorine Free * *Ammonia (R717) in industrial and food processing *R410 (operates at higher pressures) 22 * * * Coils * Filters * Dampers * Terminal units * Ducting * Air inlets & outlets MIXED AIR HEAT OUTSIDE AIR COOL * SAF SUPPLY AIR SUPPLY AIR FAN EXHAUST AIR RAF RETURN AIR RETURN AIR FAN The coils can be Refrigerant coils (DX), Hot/Chilled Water coils, or steam coils. exhaust damper Each zone is dampered. exhaust air recirc damper return air primary fan heating coil outside air outside air damper * filter cooling coil Again, a special thank you to -Building Operator Certification Program -Michael Bobker for many of the slides in this presentation *