All Fundamentals of HVAC
Wednesday, 27 July 2016
Tuesday, 26 July 2016
HVAC & R
COOLING AND HEATING EQUATIONS
SENSIBLE HEAT FACTOR & RATIO (SHR)
SUPPLY AIR FLOW RATE
AIR BALANCING EQUATIONS
CALCULATION OF HEATING AND COOLING DEGREE DAYS
FUEL CONSUMPTION BY HEATING AND COOLING UNITS
AIR CHANGE RATE EQUATION
ESTIMATING AIR LEAKAGE
VENTILATION FORMULA
ESTIMATING AIR VOLUME FOR HOODS AND ITS PRESSURE
DUCKWORK EQUATIONS
FAN EQUATIONS
PUMP EQUATION
CHILLER HEAT LOAD AND WATER FLOW
FRICTION LOSS IN WATER PIPES
COOLING TOWER
CONTROL VALVE SIZING
HEAT EXCHANGERS
HUMIDIFICATION AND DEHUMIDIFICATION
TON OF REFREGIRATION
ENERGY EFFICIENCY TERMS
DECIBLE CALCULATION
STEAM & CONDENSATE EQUATIONS
RELIEF VALVE SIZING
STEEL PIPE EQUATION
FLOW COEFFIECIENT
ELECTRICITY
SENSIBLE HEAT FACTOR & RATIO (SHR)
SUPPLY AIR FLOW RATE
AIR BALANCING EQUATIONS
CALCULATION OF HEATING AND COOLING DEGREE DAYS
FUEL CONSUMPTION BY HEATING AND COOLING UNITS
AIR CHANGE RATE EQUATION
ESTIMATING AIR LEAKAGE
VENTILATION FORMULA
ESTIMATING AIR VOLUME FOR HOODS AND ITS PRESSURE
DUCKWORK EQUATIONS
FAN EQUATIONS
PUMP EQUATION
CHILLER HEAT LOAD AND WATER FLOW
FRICTION LOSS IN WATER PIPES
COOLING TOWER
CONTROL VALVE SIZING
HEAT EXCHANGERS
HUMIDIFICATION AND DEHUMIDIFICATION
TON OF REFREGIRATION
ENERGY EFFICIENCY TERMS
DECIBLE CALCULATION
STEAM & CONDENSATE EQUATIONS
RELIEF VALVE SIZING
STEEL PIPE EQUATION
FLOW COEFFIECIENT
ELECTRICITY
STEEL PIPE EQUATIONS
A = 0.785 x ID2
WP = 10.6802 x T x (OD - T)
WW = 0.3405 x ID2
OSA = 0.2618 x OD
ISA = 0.2618 x ID
A M = 0.785 x (OD2 - ID2 )
Where
• A = Cross-Sectional Area (Sq- inches)
• WP = Weight of Pipe per Foot (Lbs)
• WW = Weight of Water per Foot (Lbs)
• T = Pipe Wall Thickness (Inches)
• ID = Inside Diameter (Inches)
• OD = Outside Diameter (Inches)
• OSA = Outside Surface Area per Foot (Sq-ft)
• ISA = Inside Surface Area per Foot (Sq-ft)
• AM = Area of the Metal (Sq-inches)
WP = 10.6802 x T x (OD - T)
WW = 0.3405 x ID2
OSA = 0.2618 x OD
ISA = 0.2618 x ID
A M = 0.785 x (OD2 - ID2 )
Where
• A = Cross-Sectional Area (Sq- inches)
• WP = Weight of Pipe per Foot (Lbs)
• WW = Weight of Water per Foot (Lbs)
• T = Pipe Wall Thickness (Inches)
• ID = Inside Diameter (Inches)
• OD = Outside Diameter (Inches)
• OSA = Outside Surface Area per Foot (Sq-ft)
• ISA = Inside Surface Area per Foot (Sq-ft)
• AM = Area of the Metal (Sq-inches)
RELIEF VALVE SIZING
RELIEF VALVE SIZING
Liquid System Relief Valves and Spring Style Relief Valves:
A = (GPM x (G)1/2 ) / [28.14 x KB x KV x ( ▲P)1/2 ]
Liquid System Relief Valves and Pilot Operated Relief Valves:
A = (GPM x (G)1/2 ) / [36.81 x KV x (▲P)1/2 ]
Steam System Relief Valves:
A = W / (51.5 x K x P x KSH x KN x KB )
Gas and Vapor System Relief Valves (Lb/Hr.):
A = (W x (TZ)1/2 ) / [C x K x P x KB x (M)1/2 ]
Gas and Vapor System Relief Valves (SCFM):
A = (SCFM x (TGZ)1/2 ) / (1.175 x C x K x P x KB )
Where
• A = Minimum Required Effective Relief Valve Discharge Area (Sq- inches)
• GPM = Required Relieving Capacity at Flow Conditions (Gallons per Minute)
• W = Required Relieving Capacity at Flow Conditions (Lbs / hr)
• SCFM = Required Relieving Capacity at Flow Conditions (Standard Cubic Feet per Minute)
• G = Specific Gravity of Liquid, Gas, or Vapor at Flow Conditions Water = 1.0 for most HVAC applications; Air = 1.0
• C = Coefficient Determined from Expression of Ratio of Specific Heats; C = 315 if Value is Unknown
• K = Effective Coefficient of Discharge; K = 0.975
• KB = Capacity Correction Factor Due to Back Pressure; KB = 1.0 for Atmospheric Discharge Systems
• KV = Flow Correction Factor Due to Viscosity; KV = 0.9 to 1.0 for most HVAC Applications with Water
• KN = Capacity Correction Factor for Dry Saturated Steam at Set Pressures above 1500 Psia and up to 3200 Psia; KN = 1.0 for most HVAC Applications
• KSH = Capacity Correction Factor Due to the Degree of Superheat; KSH = 1.0 for Saturated Steam
• Z = Compressibility Factor; Z = 1.0 If Value is Unknown
• P = Relieving Pressure (Psia); P = Set Pressure (Psig) + Over Pressure (10% Psig) + Atmospheric Pressure (14.7 Psia)
• P = Differential Pressure (Psig); P = Set Pressure (Psig) + Over Pressure (10% Psig) - Back Pressure (Psig)
• T = Absolute Temperature (°R = °F. + 460)
• M = Molecular Weight of the Gas or Vapor
Notes:
1) When multiple relief valves are used, one valve shall be set at or below the maximum allowable working pressure, and the remaining valves may be set up to 5 percent over the maximum allowable working pressure.
2) When sizing multiple relief valves, the total area required is calculated on an overpressure of 16 percent or 4 Psi, whichever is greater.
3) For superheated steam, the correction factor values listed below may be used:
• Superheat up to 400 °F: 0.97 (Range 0.979–0.998)
• Superheat up to 450 °F: 0.95 (Range 0.957–0.977)
• Superheat up to 500 °F: 0.93 (Range 0.930–0.968)
Relief Valve Vent Line Maximum Length
L = (9 x P21 x D5) / C2 = (9 x P22 x D5) / (16 x C2)
Where
• P1 = 0.25 x [(PRESSURE SETTING x 1.1) + 14.7]
• P2 = [(PRESSURE SETTING x 1.1) + 14.7]
• L = Maximum Length of Relief Vent Line (Feet)
• D = Inside Diameter of Pipe (Inches)
• C = Minimum Discharge of Air (Lbs/Min)
RELIEF VALVE SIZING
Liquid System Relief Valves and Spring Style Relief Valves:
A = (GPM x (G)1/2 ) / [28.14 x KB x KV x ( ▲P)1/2 ]
Liquid System Relief Valves and Pilot Operated Relief Valves:
A = (GPM x (G)1/2 ) / [36.81 x KV x (▲P)1/2 ]
Steam System Relief Valves:
A = W / (51.5 x K x P x KSH x KN x KB )
Gas and Vapor System Relief Valves (Lb/Hr.):
A = (W x (TZ)1/2 ) / [C x K x P x KB x (M)1/2 ]
Gas and Vapor System Relief Valves (SCFM):
A = (SCFM x (TGZ)1/2 ) / (1.175 x C x K x P x KB )
Where
• A = Minimum Required Effective Relief Valve Discharge Area (Sq- inches)
• GPM = Required Relieving Capacity at Flow Conditions (Gallons per Minute)
• W = Required Relieving Capacity at Flow Conditions (Lbs / hr)
• SCFM = Required Relieving Capacity at Flow Conditions (Standard Cubic Feet per Minute)
• G = Specific Gravity of Liquid, Gas, or Vapor at Flow Conditions Water = 1.0 for most HVAC applications; Air = 1.0
• C = Coefficient Determined from Expression of Ratio of Specific Heats; C = 315 if Value is Unknown
• K = Effective Coefficient of Discharge; K = 0.975
• KB = Capacity Correction Factor Due to Back Pressure; KB = 1.0 for Atmospheric Discharge Systems
• KV = Flow Correction Factor Due to Viscosity; KV = 0.9 to 1.0 for most HVAC Applications with Water
• KN = Capacity Correction Factor for Dry Saturated Steam at Set Pressures above 1500 Psia and up to 3200 Psia; KN = 1.0 for most HVAC Applications
• KSH = Capacity Correction Factor Due to the Degree of Superheat; KSH = 1.0 for Saturated Steam
• Z = Compressibility Factor; Z = 1.0 If Value is Unknown
• P = Relieving Pressure (Psia); P = Set Pressure (Psig) + Over Pressure (10% Psig) + Atmospheric Pressure (14.7 Psia)
• P = Differential Pressure (Psig); P = Set Pressure (Psig) + Over Pressure (10% Psig) - Back Pressure (Psig)
• T = Absolute Temperature (°R = °F. + 460)
• M = Molecular Weight of the Gas or Vapor
Notes:
1) When multiple relief valves are used, one valve shall be set at or below the maximum allowable working pressure, and the remaining valves may be set up to 5 percent over the maximum allowable working pressure.
2) When sizing multiple relief valves, the total area required is calculated on an overpressure of 16 percent or 4 Psi, whichever is greater.
3) For superheated steam, the correction factor values listed below may be used:
• Superheat up to 400 °F: 0.97 (Range 0.979–0.998)
• Superheat up to 450 °F: 0.95 (Range 0.957–0.977)
• Superheat up to 500 °F: 0.93 (Range 0.930–0.968)
Relief Valve Vent Line Maximum Length
L = (9 x P21 x D5) / C2 = (9 x P22 x D5) / (16 x C2)
Where
• P1 = 0.25 x [(PRESSURE SETTING x 1.1) + 14.7]
• P2 = [(PRESSURE SETTING x 1.1) + 14.7]
• L = Maximum Length of Relief Vent Line (Feet)
• D = Inside Diameter of Pipe (Inches)
• C = Minimum Discharge of Air (Lbs/Min)
STEAM & CONDENSATE EQUATIONS
STEAM & CONDENSATE EQUATIONS
Some common steam and condensate equations can be expressed as Steam Heating
ms = H / 960
Where
• ms = steam mass flow rate (Lbs /hr)
• H = heat flow rate (Btu/hr)
Steam Heating Liquid Flow
Ms = QL x 500 x SGL x CPL x ▲T / L S
Where
• Ms = steam mass flow rate (Lbs /hr)
• QL = volume flow liquid (GPM)
• SGL = specific heat capacity of the liquid (Btu/lb °F)
• CPL = specific gravity of the fluid
• ▲T = temperature difference liquid (°F)
• L S =latent heat of steam at steam design pressure (Btu/lb)
Steam Heating Air or Gas Flow
ms = QG x 60 x ρG x CPG x ▲TG / LS
Where
• ms = steam mass flow rate (lbs /hr)
• QG = volume flow gas (CFM)
• ρG = density of the gas (lb/ft3 )
• CPG = specific gravity of the gas (Air CPG = 0.24 Btu/Lb)
• ▲TG = temperature difference gas (0F)
• LS = latent heat of steam at steam design pressure (Btu/lb)
Steam Pipe Sizing Equations
▲P = [(0.01306 x W2 x (1+ 3.6/ID)] / (3600 x D x ID5)
W = 60 x {(P x D x ID5) / [0.01306 x (1+3.6 / ID)]}1/2
W = 0.41667 x V x AINCHES x D = 60 x V x AFEET x D
V = 2.4 x W/ AINCHES x D = W / (60 x AFEET x D)
Where
• ▲P = Pressure Drop per 100 Feet of Pipe (Psig/100 feet)
• W = Steam Flow Rate (Lbs /Hr)
• ID = Actual Inside Diameter of Pipe (Inches)
• D = Average Density of Steam at System Pres sure (Lbs/Cu-ft)
• V = Velocity of Steam in Pipe (Feet/Minute)
• AINCHES = Actual Cross Sectional Area of Pipe (Sq-inches)
• AFEET = Actual Cross Sectional Area of Pipe (Sq-ft)
Steam Condensate Pipe Sizing Equations
FS = (Hss – Hsc) / HLC x 100
WCR = FS / 100 x W
Where
• FS = Flash Steam (Percentage %)
• Hss = Sensible Heat at Steam Supply Pressure (Btu/Lb)
• Hsc = Sensible Heat at Condensate Return Pressure (Btu/Lb)
• HLC = Latent Heat at Condensate Return Pressure (Btu/Lb)
• W = Steam Flow Rate (Lbs/Hr)
• WCR = Condensate Flow based on percentage of Flash Steam created during condensing
process (Lbs/hr)
Use this flow rate in steam equations above to determine condensate return pipe size.
ms = H / 960
Where
• ms = steam mass flow rate (Lbs /hr)
• H = heat flow rate (Btu/hr)
Steam Heating Liquid Flow
Ms = QL x 500 x SGL x CPL x ▲T / L S
Where
• Ms = steam mass flow rate (Lbs /hr)
• QL = volume flow liquid (GPM)
• SGL = specific heat capacity of the liquid (Btu/lb °F)
• CPL = specific gravity of the fluid
• ▲T = temperature difference liquid (°F)
• L S =latent heat of steam at steam design pressure (Btu/lb)
Steam Heating Air or Gas Flow
ms = QG x 60 x ρG x CPG x ▲TG / LS
Where
• ms = steam mass flow rate (lbs /hr)
• QG = volume flow gas (CFM)
• ρG = density of the gas (lb/ft3 )
• CPG = specific gravity of the gas (Air CPG = 0.24 Btu/Lb)
• ▲TG = temperature difference gas (0F)
• LS = latent heat of steam at steam design pressure (Btu/lb)
Steam Pipe Sizing Equations
▲P = [(0.01306 x W2 x (1+ 3.6/ID)] / (3600 x D x ID5)
W = 60 x {(P x D x ID5) / [0.01306 x (1+3.6 / ID)]}1/2
W = 0.41667 x V x AINCHES x D = 60 x V x AFEET x D
V = 2.4 x W/ AINCHES x D = W / (60 x AFEET x D)
Where
• ▲P = Pressure Drop per 100 Feet of Pipe (Psig/100 feet)
• W = Steam Flow Rate (Lbs /Hr)
• ID = Actual Inside Diameter of Pipe (Inches)
• D = Average Density of Steam at System Pres sure (Lbs/Cu-ft)
• V = Velocity of Steam in Pipe (Feet/Minute)
• AINCHES = Actual Cross Sectional Area of Pipe (Sq-inches)
• AFEET = Actual Cross Sectional Area of Pipe (Sq-ft)
Steam Condensate Pipe Sizing Equations
FS = (Hss – Hsc) / HLC x 100
WCR = FS / 100 x W
Where
• FS = Flash Steam (Percentage %)
• Hss = Sensible Heat at Steam Supply Pressure (Btu/Lb)
• Hsc = Sensible Heat at Condensate Return Pressure (Btu/Lb)
• HLC = Latent Heat at Condensate Return Pressure (Btu/Lb)
• W = Steam Flow Rate (Lbs/Hr)
• WCR = Condensate Flow based on percentage of Flash Steam created during condensing
process (Lbs/hr)
Use this flow rate in steam equations above to determine condensate return pipe size.
DECIBEL CALCULATION
DECIBEL CALCULATION
Decibel is a logarithmic unit used to describe the ratio of the signal level - power, sound pressure,voltage, intensity, etc. Decibel is a logarithmic unit used to describe the ratio of the signal level -power, sound pressure, intensity or several other things.The decibel can be expressed as:
Decibel = 10 log (P / Pref)
Where
• P = signal power (W)
• Pref = reference power (W)
Note! Doubling the signal level increases the decibel with 3 dB (10 log (2)).
Adding Equal Sound Power Sources
The sound power and sound power level is commonly used to specify the emitted noise or sound from technical equipment as fans, pump and other machines.
The logarithmic decibel scale is convenient when calculating resulting sound power levels and sound pressure levels for two or more sound or noise sources.
Lwt = 10 log (n N / N0) = 10 log (N / N0) + 10 log (n)
= Lws + 10 log (n)
Where
• Lwt = Total sound power level (dB)
• Lws = Sound power level from each single source (dB)
• N = sound power (W)
• N0 = 10-12 - reference sound power (W)
• n = number of sources
Note: Adding two identical sources will increase the total sound power level with 3 dB (10 log (2)).
Adding Equal Sound Pressure Levels
The resulting sound pressure level when adding equal sound pressure can be expressed as:
Lpt = Lps + 20 log (n)
Where
• Lpt = total sound pres sure (dB)
• Lps = Sound pressure level from each single source (dB)
• n = number of sources
Adding Sound Power from Sources at different Levels
The sound power level from more than one source can be calculated as:
Lwt = 10 log ((N1 + N2 ... + Nn) / N0)
Decibel = 10 log (P / Pref)
Where
• P = signal power (W)
• Pref = reference power (W)
Note! Doubling the signal level increases the decibel with 3 dB (10 log (2)).
Adding Equal Sound Power Sources
The sound power and sound power level is commonly used to specify the emitted noise or sound from technical equipment as fans, pump and other machines.
The logarithmic decibel scale is convenient when calculating resulting sound power levels and sound pressure levels for two or more sound or noise sources.
Lwt = 10 log (n N / N0) = 10 log (N / N0) + 10 log (n)
= Lws + 10 log (n)
Where
• Lwt = Total sound power level (dB)
• Lws = Sound power level from each single source (dB)
• N = sound power (W)
• N0 = 10-12 - reference sound power (W)
• n = number of sources
Note: Adding two identical sources will increase the total sound power level with 3 dB (10 log (2)).
Adding Equal Sound Pressure Levels
The resulting sound pressure level when adding equal sound pressure can be expressed as:
Lpt = Lps + 20 log (n)
Where
• Lpt = total sound pres sure (dB)
• Lps = Sound pressure level from each single source (dB)
• n = number of sources
Adding Sound Power from Sources at different Levels
The sound power level from more than one source can be calculated as:
Lwt = 10 log ((N1 + N2 ... + Nn) / N0)
DECIBEL CALCULATION
Decibel is a logarithmic unit used to describe the ratio of the signal level - power, sound pressure,voltage, intensity, etc. Decibel is a logarithmic unit used to describe the ratio of the signal level -power, sound pressure, intensity or several other things.The decibel can be expressed as:
Decibel = 10 log (P / Pref)
Where
• P = signal power (W)
• Pref = reference power (W)
Note! Doubling the signal level increases the decibel with 3 dB (10 log (2)).
Adding Equal Sound Power Sources
The sound power and sound power level is commonly used to specify the emitted noise or sound from technical equipment as fans, pump and other machines.
The logarithmic decibel scale is convenient when calculating resulting sound power levels and sound pressure levels for two or more sound or noise sources.
Lwt = 10 log (n N / N0) = 10 log (N / N0) + 10 log (n)
= Lws + 10 log (n)
Where
• Lwt = Total sound power level (dB)
• Lws = Sound power level from each single source (dB)
• N = sound power (W)
• N0 = 10-12 - reference sound power (W)
• n = number of sources
Note: Adding two identical sources will increase the total sound power level with 3 dB (10 log (2)).
Adding Equal Sound Pressure Levels
The resulting sound pressure level when adding equal sound pressure can be expressed as:
Lpt = Lps + 20 log (n)
Where
• Lpt = total sound pres sure (dB)
• Lps = Sound pressure level from each single source (dB)
• n = number of sources
Adding Sound Power from Sources at different Levels
The sound power level from more than one source can be calculated as:
Lwt = 10 log ((N1 + N2 ... + Nn) / N0)
Decibel = 10 log (P / Pref)
Where
• P = signal power (W)
• Pref = reference power (W)
Note! Doubling the signal level increases the decibel with 3 dB (10 log (2)).
Adding Equal Sound Power Sources
The sound power and sound power level is commonly used to specify the emitted noise or sound from technical equipment as fans, pump and other machines.
The logarithmic decibel scale is convenient when calculating resulting sound power levels and sound pressure levels for two or more sound or noise sources.
Lwt = 10 log (n N / N0) = 10 log (N / N0) + 10 log (n)
= Lws + 10 log (n)
Where
• Lwt = Total sound power level (dB)
• Lws = Sound power level from each single source (dB)
• N = sound power (W)
• N0 = 10-12 - reference sound power (W)
• n = number of sources
Note: Adding two identical sources will increase the total sound power level with 3 dB (10 log (2)).
Adding Equal Sound Pressure Levels
The resulting sound pressure level when adding equal sound pressure can be expressed as:
Lpt = Lps + 20 log (n)
Where
• Lpt = total sound pres sure (dB)
• Lps = Sound pressure level from each single source (dB)
• n = number of sources
Adding Sound Power from Sources at different Levels
The sound power level from more than one source can be calculated as:
Lwt = 10 log ((N1 + N2 ... + Nn) / N0)
ENERGY EFFICIENCY TERMS OF REFRIGERATION SYSTEMS
ENERGY EFFICIENCY TERMS OF REFRIGERATION SYSTEMS
KW per ton
The term kW/ton is common used for large commercial and industrial air-conditioning, heat pump and refrigeration systems. The term is defined as the ratio of the rate of energy consumption in kW to the rate of heat removal in tons at the rated condition. The lower the kW/ton the more efficient is the system.
KW/ton = Pc / Hr
Where
• Ps = energy consumption (k W)
• Hr = heat removed (ton)
Coefficient of Performance-COP
The Coefficient of Performance - COP - is the basic unit less parameter used to report the efficiency of refrigerant bas ed s ystems. The Coefficient of Performance - COP - is the ratio between useful energy acquired and energy applied and can be expressed as:
COP = Hu / Ha
Where
• COP = Coefficient of performance
• Hu = Useful energy acquired (Btu)
• Ha = Energy applied (Btu)
COP can be used to define either cooling efficiency or heating efficiency as for a heat pump.
‹ For cooling, COP is defined as the ratio of the rate of heat removal to the rate of energy input to the compressor.
‹ For heating, COP is defined as the ratio of rate of heat delivered to the rate of energy input to the compressor.
COP can be used to define the efficiency at a single standard or non-standard rated condition or a weighted average seasonal condition. The term may or may not include the energy consumption of auxiliary systems such as indoor or outdoor fans, chilled water pumps, or cooling tower systems. For purposes of comparison, the higher the COP the more efficient the system.
COP can be treated as an efficiency where COP of 2.00 = 200% efficient for unitary heat pumps, ratings at two standard outdoor temperatures of 47°F and 17°F (8.3°C and -8.3°C) are typically used.
Energy Efficiency Ratio – EER
The Energy Efficiency Ratio - EER - is a term generally used to define the cooling efficiency of unitary air-conditioning and heat pump systems. The efficiency is determined at a single rated condition specified by the appropriate equipment standard and is defined as the ratio of net cooling capacity - or heat removed in Btu/h (not in tons) - to the total input rate of electric energy applied - in watt hour (not in kW). The units of EER are Btu/W-hr.
EER = Hc /Pa
Where
• EER = Energy efficient ratio (Btu/W-hr)
• Hc = net cooling capacity (Btu/hr)
• Pa = applied energy (Watts)
This efficiency term typically includes the energy requirement of auxiliary systems such as the indoor and outdoor fans and the higher the EER the more efficient is the system. Energy efficiency ratio is further categorized as Energy efficiency ratio (EER) and Seasonal energy efficiency ratio (SEER):
‹ The cooling equipment systems such as room air conditioners, heat pumps etc used in residential and small commercial buildings often express cooling system efficiency in terms of the Energy Efficiency Ratio (EER).
‹ The central air-conditioning equipment used in large residential and commercial buildings expresses cooling system efficiency in terms of the Seasonal Energy Efficiency Ratio (SEER).
Recommended selection of room air conditioners is EER of at least 9.0 for mild climates and over 10 for hot climates and for central air conditioning system it is tested to be as high as 17 units. The U.S. Government's minimum efficiency level is 10 SEER for split systems and 9.7 for packaged units.
Efficiency - Heating Systems
Turndown Ratio = Maximum Firing Rate: Minimum Firing Rate (i.e., 5:1, 10:1, 25:1)
Overall Thermal Efficiency = (Gross Btu Output / Gross Btu Input) x 100%
• Overall Thermal Efficiency Range 75%–90%
Combustion Efficiency = {(Btu Input – Btu Stack Loss) / Btu Input} x 100%
• Combustion Efficiency Range 85%–95%
ENERGY EFFICIENCY TERMS OF REFRIGERATION SYSTEMS
KW per ton
The term kW/ton is common used for large commercial and industrial air-conditioning, heat pump and refrigeration systems. The term is defined as the ratio of the rate of energy consumption in kW to the rate of heat removal in tons at the rated condition. The lower the kW/ton the more efficient is the system.
KW/ton = Pc / Hr
Where
• Ps = energy consumption (k W)
• Hr = heat removed (ton)
Coefficient of Performance-COP
The Coefficient of Performance - COP - is the basic unit less parameter used to report the efficiency of refrigerant bas ed s ystems. The Coefficient of Performance - COP - is the ratio between useful energy acquired and energy applied and can be expressed as:
COP = Hu / Ha
Where
• COP = Coefficient of performance
• Hu = Useful energy acquired (Btu)
• Ha = Energy applied (Btu)
COP can be used to define either cooling efficiency or heating efficiency as for a heat pump.
‹ For cooling, COP is defined as the ratio of the rate of heat removal to the rate of energy input to the compressor.
‹ For heating, COP is defined as the ratio of rate of heat delivered to the rate of energy input to the compressor.
COP can be used to define the efficiency at a single standard or non-standard rated condition or a weighted average seasonal condition. The term may or may not include the energy consumption of auxiliary systems such as indoor or outdoor fans, chilled water pumps, or cooling tower systems. For purposes of comparison, the higher the COP the more efficient the system.
COP can be treated as an efficiency where COP of 2.00 = 200% efficient for unitary heat pumps, ratings at two standard outdoor temperatures of 47°F and 17°F (8.3°C and -8.3°C) are typically used.
Energy Efficiency Ratio – EER
The Energy Efficiency Ratio - EER - is a term generally used to define the cooling efficiency of unitary air-conditioning and heat pump systems. The efficiency is determined at a single rated condition specified by the appropriate equipment standard and is defined as the ratio of net cooling capacity - or heat removed in Btu/h (not in tons) - to the total input rate of electric energy applied - in watt hour (not in kW). The units of EER are Btu/W-hr.
EER = Hc /Pa
Where
• EER = Energy efficient ratio (Btu/W-hr)
• Hc = net cooling capacity (Btu/hr)
• Pa = applied energy (Watts)
This efficiency term typically includes the energy requirement of auxiliary systems such as the indoor and outdoor fans and the higher the EER the more efficient is the system. Energy efficiency ratio is further categorized as Energy efficiency ratio (EER) and Seasonal energy efficiency ratio (SEER):
‹ The cooling equipment systems such as room air conditioners, heat pumps etc used in residential and small commercial buildings often express cooling system efficiency in terms of the Energy Efficiency Ratio (EER).
‹ The central air-conditioning equipment used in large residential and commercial buildings expresses cooling system efficiency in terms of the Seasonal Energy Efficiency Ratio (SEER).
Recommended selection of room air conditioners is EER of at least 9.0 for mild climates and over 10 for hot climates and for central air conditioning system it is tested to be as high as 17 units. The U.S. Government's minimum efficiency level is 10 SEER for split systems and 9.7 for packaged units.
Efficiency - Heating Systems
Turndown Ratio = Maximum Firing Rate: Minimum Firing Rate (i.e., 5:1, 10:1, 25:1)
Overall Thermal Efficiency = (Gross Btu Output / Gross Btu Input) x 100%
• Overall Thermal Efficiency Range 75%–90%
Combustion Efficiency = {(Btu Input – Btu Stack Loss) / Btu Input} x 100%
• Combustion Efficiency Range 85%–95%
HUMIDIFICATION & DEHUMIDIFICATION
HUMIDIFICATION & DEHUMIDIFICATION
HUMIDIFICATION
GRreqd = (WGR/ SpV) Room air – (WGR / SpV) Supply Air
Lbreqd = (Wlb / SpV) Room air – (Wlb / SpV) Supply Air
Qsteam = (Qair x GRreqd x 60) / 7000
Qsteam = Qair x Lbreqd x 60
Where
• GRreqd = Grains of Moisture Required (Gr H2O per Cu-ft of air)
• Lbreqd = Pounds of Moisture Required (Lb H2O per Cu-ft of air)
• Qair = Air Flow Rate (CFM)
• Qsteam = Steam Flow Rate (Lb per hour)
• SpV = Specific Volume of Air (Cu-ft per lb of dry air)
• ▲Wlb = Specific Humidity (lb-H2O per lb of dry air)
• ▲WGr = Specific Humidity (Gr. H2O per lb of dry air)
Humidifier Sensible Heat Gain
GRreqd = (WGR/ SpV) Room air – (WGR / SpV) Supply Air
Lbreqd = (Wlb / SpV) Room air – (Wlb / SpV) Supply Air
Qsteam = (Qair x GRreqd x 60) / 7000
Qsteam = Qair x Lbreqd x 60
Where
• GRreqd = Grains of Moisture Required (Gr H2O per Cu-ft of air)
• Lbreqd = Pounds of Moisture Required (Lb H2O per Cu-ft of air)
• Qair = Air Flow Rate (CFM)
• Qsteam = Steam Flow Rate (Lb per hour)
• SpV = Specific Volume of Air (Cu-ft per lb of dry air)
• ▲Wlb = Specific Humidity (lb-H2O per lb of dry air)
• ▲WGr = Specific Humidity (Gr. H2O per lb of dry air)
Humidifier Sensible Heat Gain
H = (0.244 x Q x ▲T) + (L x 380)
Where
• H = Sensible Heat Gain (Btu/Hr)
• Q = Steam Flow (Lb-Steam/Hr)
• ▲T = Steam Temperature - Supply Air Temperature (°F)
• L = Length of Humidifier Manifold (ft)
DEHUMIDIFIER EQUATIONS
A measure of the capacity of a dehumidifier is expressed in lbs per hour of moisture removal and is estimated by equation:
MRC = [Qair x (60 min/hr / Vs] x (GPPin - GPPout )) / 7000 grains/lb
Where,
• MRC = Moisture removal capacity (in Lb /hr)
• Qair = Volumetric rate of air (CFM)
• Vs = Specific volume of air (Cu-ft / lb)
• GPPin = Grains of moisture per pound of dry air in the inlet air stream
• GPPout = Grains of moisture per pound of dry air in the outlet air stream
The difference in (GPPin – GPPout) represents the grain "depression" or removal across the
dehumidifier.
Where
• H = Sensible Heat Gain (Btu/Hr)
• Q = Steam Flow (Lb-Steam/Hr)
• ▲T = Steam Temperature - Supply Air Temperature (°F)
• L = Length of Humidifier Manifold (ft)
DEHUMIDIFIER EQUATIONS
A measure of the capacity of a dehumidifier is expressed in lbs per hour of moisture removal and is estimated by equation:
MRC = [Qair x (60 min/hr / Vs] x (GPPin - GPPout )) / 7000 grains/lb
Where,
• MRC = Moisture removal capacity (in Lb /hr)
• Qair = Volumetric rate of air (CFM)
• Vs = Specific volume of air (Cu-ft / lb)
• GPPin = Grains of moisture per pound of dry air in the inlet air stream
• GPPout = Grains of moisture per pound of dry air in the outlet air stream
The difference in (GPPin – GPPout) represents the grain "depression" or removal across the
dehumidifier.
HUMIDIFICATION & DEHUMIDIFICATION
HUMIDIFICATION
GRreqd = (WGR/ SpV) Room air – (WGR / SpV) Supply Air
Lbreqd = (Wlb / SpV) Room air – (Wlb / SpV) Supply Air
Qsteam = (Qair x GRreqd x 60) / 7000
Qsteam = Qair x Lbreqd x 60
Where
• GRreqd = Grains of Moisture Required (Gr H2O per Cu-ft of air)
• Lbreqd = Pounds of Moisture Required (Lb H2O per Cu-ft of air)
• Qair = Air Flow Rate (CFM)
• Qsteam = Steam Flow Rate (Lb per hour)
• SpV = Specific Volume of Air (Cu-ft per lb of dry air)
• ▲Wlb = Specific Humidity (lb-H2O per lb of dry air)
• ▲WGr = Specific Humidity (Gr. H2O per lb of dry air)
Humidifier Sensible Heat Gain
GRreqd = (WGR/ SpV) Room air – (WGR / SpV) Supply Air
Lbreqd = (Wlb / SpV) Room air – (Wlb / SpV) Supply Air
Qsteam = (Qair x GRreqd x 60) / 7000
Qsteam = Qair x Lbreqd x 60
Where
• GRreqd = Grains of Moisture Required (Gr H2O per Cu-ft of air)
• Lbreqd = Pounds of Moisture Required (Lb H2O per Cu-ft of air)
• Qair = Air Flow Rate (CFM)
• Qsteam = Steam Flow Rate (Lb per hour)
• SpV = Specific Volume of Air (Cu-ft per lb of dry air)
• ▲Wlb = Specific Humidity (lb-H2O per lb of dry air)
• ▲WGr = Specific Humidity (Gr. H2O per lb of dry air)
Humidifier Sensible Heat Gain
H = (0.244 x Q x ▲T) + (L x 380)
Where
• H = Sensible Heat Gain (Btu/Hr)
• Q = Steam Flow (Lb-Steam/Hr)
• ▲T = Steam Temperature - Supply Air Temperature (°F)
• L = Length of Humidifier Manifold (ft)
DEHUMIDIFIER EQUATIONS
A measure of the capacity of a dehumidifier is expressed in lbs per hour of moisture removal and is estimated by equation:
MRC = [Qair x (60 min/hr / Vs] x (GPPin - GPPout )) / 7000 grains/lb
Where,
• MRC = Moisture removal capacity (in Lb /hr)
• Qair = Volumetric rate of air (CFM)
• Vs = Specific volume of air (Cu-ft / lb)
• GPPin = Grains of moisture per pound of dry air in the inlet air stream
• GPPout = Grains of moisture per pound of dry air in the outlet air stream
The difference in (GPPin – GPPout) represents the grain "depression" or removal across the
dehumidifier.
Where
• H = Sensible Heat Gain (Btu/Hr)
• Q = Steam Flow (Lb-Steam/Hr)
• ▲T = Steam Temperature - Supply Air Temperature (°F)
• L = Length of Humidifier Manifold (ft)
DEHUMIDIFIER EQUATIONS
A measure of the capacity of a dehumidifier is expressed in lbs per hour of moisture removal and is estimated by equation:
MRC = [Qair x (60 min/hr / Vs] x (GPPin - GPPout )) / 7000 grains/lb
Where,
• MRC = Moisture removal capacity (in Lb /hr)
• Qair = Volumetric rate of air (CFM)
• Vs = Specific volume of air (Cu-ft / lb)
• GPPin = Grains of moisture per pound of dry air in the inlet air stream
• GPPout = Grains of moisture per pound of dry air in the outlet air stream
The difference in (GPPin – GPPout) represents the grain "depression" or removal across the
dehumidifier.
Subscribe to:
Posts (Atom)