STP & ETP

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  STP     Sewage treatment platn (residential & commercial) ETP     Effluent treatment plant (industry) COD     Chemical oxygen demand (soluble & insoluble organic compound) (2hr to 3hr) (mg/l) BOD     Biochemical oxygen demand (organic compound) (3days to 5days) (mg/l) KEY POINTS: Outlet of STP 50mg/l Biproduct of anaerobic digestion is H2S & NH3 To reduce stink smell use ozone 
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HVAC SYSTEM

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                            HVAC SYSTEM

SOME IMPORTANT ABBREVIATIONS USED IN HVAC SYSTEM ARE

  • HVAC        Heating ventilation and air conditioning
  • CAV           Constant air volume                   
  • VAV           Variable air volume 
  • VRV           Variable refrigerant volume
  • VRF           Variable refrigerant flow
  • ACC           Air cooled chiller          
  • WCC          Water colled chiller   
  • FCU           Fan coil unit            
  • AHU          Air handling unit 
  • DTA           Draw through AHU
  • BTA           Blow through AHU
  • HEPA         High efficiency particulates arrestence
  • PACU        Precision air conditioning unit
  • CSU           Ceiling suspended unit
  • VFD          Variable frequency drive
  • CFM           Cubic feet per minute
  • TR              Ton of refrigeration
  • BTU           British thermal unit
  • DBT           Dry bulb temperature
  • WBT          Wet bulb temperature
  • DPT            Dew point temperature
  • COP            Coefficient of performance
  • EER            Energy efficiency ratio

AIR CONDITIONING TYPES BASED ON GAS REFRIGERANT

  • window
  • portable 
  • split 
  • cassette unit
  • ductable
  • precision air conditioning unit
  • wall ceiling unit or ceiling suspended unit
  • VRV/VRF air handling unit

AIR CONDITIONING TYPES BASED ON CHILL WATER SUPPLY

  • air handling unit  
  • fan coil unit

KEY POINTS

  • In constant air volume the damper position should be fixed constant.
  • In variable air volume the damper position can be varied at any instant.
  • Variable refrigerant volume is trade marked by Daikin brand where multiple indoor units are connected by using only one outdoor unit.
  • Variable refrigerant flow is trade marked by rest of the brands where multiple indoor units are connected by using only one outdoor unit.
  • Air cooled chiller should be placed in terrace.
  • Water cooled chiller should be placed in ground floor or basements.
  • Tonnage rating of split (1-2.5)TR
  • Tonnage rating of cassette unit (1.5-4)TR
  • Tonnage rating of ductable unit (2.5-12)TR
  • Tonnage rating of PACU (8-16)TR
  • Tonnage rating of CSU (12-20)TR
  • TR means amount of heat extracted to produce one ton of ice.
  • CFM means volume of air entering the room in a minute.
  • Types of filters are fibreglass, polyester, washable & hepa(high efficiency particulates arrestence)
  • Humidity types: Absolute, Relative & Specific
  • SI unit of temperature is Kelvin (K) 0K = -273'C
  • DBT is the ambient air temperature
  • WBT is always between the DBT & DPT
  • DPT is the temperature where water vapour starts to condense out of the air (the tempeature at which air becomes completely saturated). Above this temperature the moisture stays in the air. If the DPT is close to the dry air temperature then RH is high. If the DPT is well below the dry air temperature then RH is low.
  • Delta T is the temperature difference between chiller water inlet & outlet temperature (Normally it should not be more than 5'C)
  • IKW = KW / TR (system is more efficient as low value as IKW 0.7 to 0.5 is excellent)
  • COP = 3.516 / IKW ( > 5 is excellent)
  • EER = COP * 3.412
  • Indoor air quality standards : CO2 1000 ppm max , CO 3 to 4 , RH 25% to 60% , Temp 20'C to 24'C & 30% fresh air supply
  • 1 TR = 400 CFM (for centralized air conditioning system)
  • 1 TR = 300 CFM (for non centralized air conditioning system)
  • 1 TR = 12000 Btu/h
  • 1 TR = 3.516 thermal KW
  • 1 TR = 3024 kcal/h
  • TR = (chilled water flow in m3/h * specific heat * difference in temp in 'C) / (3024) where, density of water (specific heat) = 1000 kg/m3 , difference in temp = (13-7.7) & chilled water flow = 189 we get 331 TR
  • 1 KW = 3412 Btu/h
  • 3.4192 * W = Btu/h
  • Human 400 Btu/h
  • Total Heat load = Room area BTU + Total occupant BTU + Equipment BTU + Lightning BTU. wherer, total occupant btu = no of occupatn * 400 & room area btu = length (m) * width (m) * 337


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