HVAC Control in the New Millennium.pdf - HVAC.Amickracing

HVAC Control in the New Millennium1. The total heat to be removed from both the gases and water vapor.2. The sensible heat removed from the air.3. The latent heat removed in condensing the water vapor.Total heat = cubic feet/minute × 4.5 (h 1 - h 1 )= Btu/hourSensible heat = cubic feet/minute × 1.08 db 1 - db 1 )= Btu/hourLatent heat = cubic feet/minute × 68 (wb 1 - wb 2 )= Btu/hourwhere, h 1 = total heat for entering air, Btu/poundh 2 = total heat for leaving air, Btu/pounddb 1 = entering air dry-bulb temperaturedb 2 = leaving air dry-bulb temperaturewb 1 = entering air wet-bulb temperaturewb 2 = leaving air wet-bulb temperatureMost heating and air conditioning calculations are made assumingsea-level pressure and standard temperatures, but high altitude or hightemperature applications will require converting from standard conditionsto those actually present.Comfort ChartsBecause of the possibility of shock to the human system, it is notdesirable to have too great a difference between indoor and outdoortemperatures, particularly in the summer. Also, from the standpoint ofphysical comfort, low humidity with high temperature is comparable tohigh humidity at lower temperatures.The greatest physical comfort in cold weather without undue hightemperatures is achieved by increasing the humidity of the conditionedarea. This also explains why some parts of the country are not extremelyuncomfortable even though the outside air temperature is 100°F or morewith a low relative humidity.©2001 by The Fairmont Press, Inc. All rights reserved.