Chapter 8 Internal Forced Convection8-43Air enters the constant spacing between the glass cover and the plate of a solar collector. The net rate of heat transfer and the temperature rise of air are to be determined. Assumptions1Steady operating conditions exist. 2The inner surfaces of the spacing are smooth. 3Air is an ideal gas with constant properties. 4 The local atmospheric pressure is 1 atm. PropertiesThe properties of air at 1 atm and estimated average temperature of 35°C are (Table A-15) /sm10655.1CW/m.02625.0kg/m146.125-3×=υ°==ρk7268.0PrCJ/kg.1007=°=pCAnalysisMass flow rate, cross sectional area, hydraulic diameter, mean velocity of air and the Reynolds number are Air 30°C 0.15 m3/min 60°C Collector plate (insulated) Glass cover 20°C kg/s1719.0)/sm15.0)(kg/m146.1(33===Vm&&ρAc==(1 m)(0.03 m)m2003.DAPhc+=44003210 05825(..m)m m)m2VVAmc=&.0155m/s0.03 mm/s32606,17/sm10655.1m)25m/s)(0.058(5Re25=×==−υhmDVwhich is greater than 10,000. Therefore, the flow is turbulent and the entry lengths in this case are roughly
This is the end of the preview. Sign up
access the rest of the document.
This note was uploaded on 01/22/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.