1. Lecture Objectives: Specify Exam Time Finish with HVAC systems –HW3 Introduce Projects 1 & 2 –eQUEST –other options

2. Example Available capacity as function of evaporator and condenser temperature Equipment Selection example Need 1.2 ton Of water cooling 1 ton = 12000 Btu/h Capacity is 1.35 ton only for: 115 F air condenser temp 50 F of water temperature

3. Modeling of Chiller Chiller model acronyms: Available capacity as function of evaporator and condenser temperature Full load efficiency as function of condenser and evaporator temperature Efficiency as function of percentage of load Part load: The consumed electric power [KW] under any condition of load Part Load Ratio Energy Input Ratio as Function of Part Load Ratio Energy Input Ratio as Function of Temperature CAPacity as Function of Temperature

4. HW3 Chiller model: COP= f(T OA, Q cooling, chiller properties) Chiller data: Q NOMINAL nominal cooling power, P NOMINAL electric consumption for Q NOMINAL Cooling water supplyOutdoor air Full load efficiency as function of condenser and evaporator temperature Efficiency as function of percentage of load Percentage of load: The coefficient of performance under any condition: The consumed electric power [KW] under any condition Available capacity as function of evaporator and condenser temperature

5. Air-conditioning in Air Handling Unit (AHU) Compressor and Condenser Roof top AHU Gas/Electric Heater to building Fan air from building fresh air Evaporator filter mixing hot water cool water Return fan Supply fan flow control dampers AHU Fresh air AHU schematic Outdoor air To room ExhaustFrom room

6. Processes in AHU presented in Psychrometric in psychrometric OA Case for Summer in Austin IA MA SA

7. Building-System-Plant Plant (boiler and/or Chiller) Building HVAC System (AHU and distribution systems)

8. Integration of HVAC and building physics models Building Heating/Cooling System Plant Building Heating/Cooling System Plant Load System Plant model Integrated models Q buiolding Q including Ventilation and Dehumidification

9. System Models: Schematic of simple air handling unit (AHU) m - mass flow rate [kg/s], T – temperature [C], w [kg moist /kg dry air ], r - recirculation rate [-], Q energy/time [W] Mixing box

10. Energy and mass balance equations for Air handling unit model – steady state case m S is the supply air mass flow rate c p - specific capacity for air, T R is the room temperature, T S is the supply air temperature. w R and w S are room and supply humidity ratio - energy for phase change of water into vapor The energy balance for the room is given as: The air-humidity balance for room is given as: The energy balance for the mixing box is: ‘r’ is the re-circulated air portion, T O is the outdoor air temperature, T M is the temperature of the air after the mixing box. The air-humidity balance for the mixing box is: w O is the outdoor air humidity ratio and w M is the humidity ratio after the mixing box The energy balance for the heating coil is given as: The energy balance for the cooling coil is given as:

12. Project 1: Use eQUEST software to model an example building Use it in simple and detailed modes

13. Project 2: HVAC Topics

14. Heat Recovery Systems Air to Air Heat Exchanger Plate heat exchangers Enthalpy wheelEffectiveness ~60% Effectiveness ~75% Effectiveness ~50%

15. Ventilation Heat Recovery Systems for cooling and heating Commercial buildings Residential buildings Saving % - depends on how much ventilation we have in the building

16. Water Cooled Chiller Outside air 95°F Inside 75°F Water 42°F Building Water 52°FWater 120°F Water 100°F Cooling tower Chiller Task: analyze COP for the whole year and different locations

17. Solar hot water system

18. Geothermal Energy Systems (in combination with a cooling machine / heat pump) Summer Winter In the summer, the earth acts as a cooling tower. The Cooling Machine loads the loop with heat, sending warmed water to be cooled by the earth In the winter, the earth acts as the boiler. The Heat Pump extracts heat from the loop, sending cooled water to be warmed by the earth.