Some BasicHVAC

First Law of Thermodynamics

H = U + PV

Enthalpy

Second Law: Entropy

HVAC - Cooling

dS = dQ/T

Second Law: Entropy HVAC - Cooling

COP – dimensionless! –

EER – dimensions of

Btu/h/W!

HVAC - Cooling

ideal

evQ

kpH’

COP = evQ / kpH’ = (h1-h4) / (h2-h1)

evQ

kpH’

HVAC - Cooling

Cooling Rates

1. evTT cooling flow rate= evQBtu/h, cooling flow / 12000 Tons to Btu/h conversion

2. evQ Btu/h cooling flow rate = acF´ kW elec Power to AC * e * b * 3412. * COP see Spread Sheet

3. kpH´Btu/h Heat equ. Power to Ko = acF´ kW elec Power to AC * e * b * 3412.

4. kpF´ kW elec Power to Komp = acF´ kW elec Power to AC * e * b

5. kpH´ Btu/h Heat equ. Power to Komp = kpF´ kW elec Power to Komp * 3412electrical HV

6. COP = evQBtu/h, Rate of heat absorbed / kpH´Btu/h, work to compresssor practical COP (heat loss incl)

7. COPH = cdQBtu/h, condenser / kpH´Btu/h Btu/h COP HEATPUMP defined

8. EERBtu/Wh = evQBtu/h, Rate of heat absorbed / kpF´WW, Total Power input EER defined

9. EERBtu/Wh = COP * 3.412Btu/h / W EER in terms of COP

10. kpF´kw = kpF´Ww / 1000

11. kW|T = acF´kW elec Power to AC / evTTons cooling rate produced by AC kw per Ton

12. kW|T = 12000Btu/h/T / (3412Btu/h/kW * COP) kW per Ton as f of COP

13. kWh|Th = 12000. / (3412. * COP) kWh per Tonh

14. kW|T = 12k Btu/h/T / EERBtu/Wh kW per Ton as f of EER

15. abH´Btu/h, equ. Heat to generator - = mstlb/h of steam, * hfgBtu/lb, 955 1-stage, 860 2-stage Absorption thermal Power to Generator (Absorption chiller)

Nipuna

COP = evQ / kpH’ = (h1-h4) / (h2-h1)

HVAC - Cooling

Stay away from Window Air Conditioner

HVAC - Cooling

Split System

HVAC - Cooling

Chilled-water System

Cooling Tower

HVAC - Cooling

Reciprocating Compressor Scroll Compressor

Chilled-water System

HVAC - Cooling

Chilled-water System: Centrifugal Compressor

Chilled-water System

HVAC - Cooling

Rooftop Units

HVAC - Cooling

Rooftop Units

HVAC - Cooling

Rooftop Units

HVAC - Cooling

Saturation humidity line: Wet bulb temperature lines Relative humidity line

Specific volume lines Enthalpy lines

Psychrometric Chart

HVAC - Cooling

HVAC - Cooling

The energy efficiency rating (EER) of an air conditioner is its BTU/h rating over its Wattage.

Example: window air conditioner Rating: 10,000-BTU/h Power Consumption: 1,200 watts EER = 10,000 BTU/h/1,200 watts = 8.3 Btu/Wh

Normally a higher EER is accompanied by a higher price.

HVAC - Cooling

Choice between two 10,000-BTU/h units

1. EER of 8.3, consumes 1,200 watts2. EER of 10, consumes 1000 watts.

Price difference is $100. Usage: 4 months a year, 6 hours a day. Electricity Cost: $0.10/kWh. ===========================================4 mo. x 30 days/mo. x 6 hr/day = 720 hours

(720 h x .2 kW) x $0.10/kWh = $14.40 Savings

Since the EER 10 unit costs $100 more, it will take about seven years for this more expensive unitto break even

HVAC - Cooling

HVAC - Cooling

HVAC - Cooling

HVAC -Heating

High Efficiency Upflow Furnace

Efficiency: .8 - .95

FIRETUBE BOILER

HVAC -Heating

FIRETUBE BOILERS WATERTUBE BOILERS

Disadvantages of the Watertube design include:High initial capital cost Cleaning is more difficult due to the design No commonality between tubes Physical size may be an issue

Disadvantages of Firetube Boilers include:Not suitable for high pressure applications 250 psig and above Limitation for high capacity steam generation

HVAC -Heating

Scotch Boiler

HVAC -Heating

HVAC -Heating

HVAC -Heating

Thermostatic Steam Traps

Mechanical Steam Traps 

HVAC -Heating

Thermodynamic Steam Traps 

Orifice Steam Traps 

HVAC -Heating

Determination of Efficiency 

HVAC -Heating

HVAC -Heating

HVAC -Heating

HVAC Motors

Radial Flow belt driven Fan

Radial Flow belt driven Fan

HVAC Fans

B = C + A

velocity p

Total p

static dp

HVAC Motors

HVAC Motors

Variable Frequency Drive is closest to Centrifugal Fan Law

HVAC Motors

Variable Speed Drive

HVAC Motors

HVAC –Ventilation

Distribution System and Controls

Circulation Systems

HVAC –Ventilation

Circulation Systems

Two Duct System

HVAC –Ventilation

Four Pipe Systems

Circulation Systems

HVAC –Ventilation

HVAC - Envelope

Building Envelope

Heat Flow

1. hQBtu/h, W Heat flow = Aft2, m2 * TF, C / R(F*ft2*h)/(Btu) , (C*m2/W) Heat Flow as function of Thermal Resistance R

2. hQ Btu/h, W Heat flow = Aft2, m2 * C Btu/(h*ft2*F), W/(m2 *C) * TF, C Heat Flow (loss) in terms of Conductance C

3. hQBtu/h, W = Aft2, m2 * (kBtu/(h*ft*F, W/ (m*C) / Lft, m) Btu/(h*ft2*F) , W/(m2 *C) * TF, C Heat Loss (flow) in terms of conductivity k

Heat Flux

4. hqBtu/(h*ft2), W/m2 Heat flux = TF, C / R(F*ft2*h)/(Btu) , (C*m2/W) Heat flux as function of R

5. hq Btu/h*ft2), W/m2 Heat flux = C Btu/(h*ft2*F), W/(m2 *C) Conductance * TF, C Heat flux as function of C

6. hqBtu/h*ft2), , W/m2 Heat flux = k Btu/(h*ft*F),conductivity, W/(m*C) / Lft,m * TF, C Heat flux as function of k

R – C – k

7. R (F*ft2*h)/(Btu) , (C*m2/W) = 1 / C Btu/(h*ft2*F) , W/(m2 *C) R –C Relationship

8. C Btu/(h*ft2*F), W/(m2 *C) = k Btu/(h*ft*F), W/(m*C) / Lft, m C – k Relationship

9. R(F*ft2*h)/(Btu) , (C*m2/W) = Lft, m / k Btu/(h*ft*F) , W/(m*C) R – k Relationship

Convenience Conductivity k´, per inch, per cm

10. hQBtu/h, W = Aft2, cm2 * (k´Btu*in/(h*ft2*F), W/cm*C / L´in, cm) Btu/(h*ft2*F), W/(cm2*C) * TF C Heat flow (loss) in terms of convenience k

11. hqBtu/h*ft2), Heat flux = k´ Btu*in/(h*ft2*F),conductivity / L´in * TF Heat flux and convenience k

12. C Btu/(h*ft2*F), = k´ Btu*in/(h*ft2*F) / L´in C – convenience k Relationship

13. R(F*ft2*h)/(Btu) = L´in / k´ Btu*in/(h*ft2*F) R – convenience kRelationship

Convenience Resistance R´ – R per inch, cm

14. R´ (h*ft2*F) / (Btu * in) = (h*ft2*F) /Btu / in , (cm * C) / W = 1 / k´ Btu*in/(h*ft2*F), W/cm*C R´ per inch, cm = R / L´ = (L / k ) / L´ , L´ cm, in

15. R(F*ft2*h)/(Btu), (C*m2/W) = R´ (h*ft2*F) / (Btu * in), (cm * C) / W * L´in, cm R = R´ * L´

Building Envelope Nipuna en:p:ÙN:

HVAC - Envelope

Building Envelope Nipuna en:p:ÙN:

HVAC - Envelope

Building Envelope – HDD/CDD Data

HVAC - Envelope

Building Envelope

Values from G. Pita

“Air Conditioning and Principles”, 2002

HVAC - Envelope

Building Envelope NY Data

HVAC - Envelope

Building Envelope NY Data

HVAC - Envelope

Windows

HVAC - Envelope

Windows

HVAC - Envelope

eQuest and Power DOE

Modeling