A 2 x 2 m flat plate solar collector for domestic hot water heating is shown in the figure. The incident solar radiation on the glass cover, which transmits 90% of the incident flux, is 750 W/m2. Water flows through the tubes soldered to the backside of the absorber plate, entering at a temperature of 25°C. The temperature of the glass cover is 27°C, and it radiates heat with an emissivity of 0.92 to the sky at –50°C. Additionally, the glass cover losses heat by convection to air at 20°C flowing over its surface at 30 km/h. Assume that the radiation heat transfer between the absorber plate and glass cover and the heat transfer through the back and sides of the collector is negligible.

On a summer day, the mean solar irradiance received at a lake was 500 W/m^ 2 over 25 days (consider the day length to be 8 hours). If 80% of the energy is used to vaporize water, how large could the depth of evaporation be?

The room pictured has the following absorption coefficients at 500 Hz: Floor: Carpet, α = 0.14 Ceiling: Acoustic Ceiling Tile, α = 0.70 Walls: Gypsum Wallboard, α = 0.10 Reference image attached below. a. Calculate the total absorption in this room b. Calculate the room constant. c. Calculate the critical distance. Assume Q=4. d. A source generates a sound power level, LW, of 102 dB. The directivity, Q, is 4. What sound pressure level, Lp, would be measured at a distance of 6 m in the room above?