4 Outside Air Enters The Inlet Of A Hvac System At A Dry Air Flow Rate Of 0 25 Kg S And A Temperature Of 28 C And A Re 1 (121.25 KiB) Viewed 48 times
4. Outside air enters the inlet of a HVAC system at a dry air flow rate of 0.25 kg/s and a temperature of 28 °C and a relative humidity (0) of 60%. The air leaves the heat exchanger at a temperature of 14 °C and a relative humidity (0) of 100%. Assume that the air pressure is equal to 1.01325 bar. (a) Write the first law energy balance around the HVAC system shown below. (b) Determine the heat transfer rate from the air as it moves across the heat exchanger. (do hand calculations for 01 and 02 and show your work) (c) Determine the hourly flow rate of water condensed from the air (show your work). (d) Use to attached psychrometric chart to estimate 01, 02, hy and h2. Show your work. You can assume Cp,air = 1.005 kJ/kg/K. T(°C) Psat (bar) hair(kJ/kg) hg(kJ/kg) he(kJ/kg) 28 0.03782 0.6 301.34 2552.6 14 0.01598 1 287.3 2527.1 58.8 Qdot,out = ? mair = 0.25 kg/s = 0.6 T= 28 °C mair = 0.25 kg/s 0 = 1.00 T = 14 °C mwATER = ?, T = 14 °C
kg water/kg dry air Humidity ratio, ' .030 .028 .026 -.024 .022 008 900- >00:- 002 .000 SO 0.95 Specific volume, /kg dry air 0.90 90 Dry bulb temperature, °C 20 208 0.85 100 Wet bulbor saturation temperature. 90 80 02 2țe kap 6X/ og 10 Specific enthalpy of moist air, 0 19 ON 29 10 01- Figure A-4 Psychrometric chart for 1 atm (SI units). Source: Z. Zhang and M. B. Patc. "A Mcthodology for Implementing a Psychrometric Chart in a Computer Graphics System," ASTRAE Transactions, Vol. 94. Pt. 1, 1988.
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