Lecture Objectives: Review Psychrometrics Introduce Air Handling Unit Analyze swimming pool dehumidification example

HW1 Psychrometrics Due: September 18 Textbook (Thermal Environmental Engineering) problems: 8.1, 8.8, 8.13, 8.20 You have posted section 8 of this book

Psychrometric Chart Need two quantities for a state point Can get all other quantities from a state point Can do all calculations without a chart Often require iteration Many “digital” psychrometric charts available Can make your own Best source is ASHRAE fundamentals (Chapter 6)

Connection between W and Pw (W humidity ratio – Pw water partial pressure) PV = mRT (Ideal Gas Law ) P = Pw + Pa R = gas constant P = pressure V = volume T = absolute temperature W = humidity ratio Subscripts: w is water vapor, a is dry air

Psychrometrics (Swimming pool example)

Swimming pool energy and mass balance

Evaporation Heat loss by evaporation: hm Tpool Tair pool W s W ≈ hm Ws Tpool Wair pool Depends on the air speed and even more on the condition of the water surface (people splashing in the water) Further analysis can be conducted in the psychrometric chart

Air handling units (AHUs) Major components - …..

Major AHU Components Heat Exchangers Humidifiers Steam Air to air Water Water (mist) AHU Fans Air - water or air - refrigerate Many more …

Positioning of AHUs Distribution systems Fresh air AHU For ventilation AHU – Air Handling Unit Distribution systems Fresh air For ventilation AHU Primary systems Air transport Electricity Secondary systems Cooling (chiller) Heating (boilers) Building (or Gas) Gas

Process in AHUs Example AHUs for swimming pools MENERGA ThermoCond 19

Swimming pool heating

Dehumidification using outside air in Winter and Summer

More advance control MENERGA ThermoCond 29

Dehumidification using outside air in winter Condenser in the air stream Evaporator Compressor of the heat pump Condenser in the swimming pool

Recirculation of air with dehumidification catalog