Residential annual energy use. For a house with: Air exchange rate of 0.5 h−1 Cp = 1000 J/kg.K Density of air = 1.2 kg/m3 Roof area = 144 m2; opaque wall area = 96 m2; window area = 24 m2; volume = 360 m3 Conductivity of Uwall = 0.60 W/(m2-K); Uwin = 3.0 W/(m2-K); Uroof = 0.40 W/(m2-K) Heating system efficiency of 0.85 Heating degree days (HDD) of 3500 K-days Calculate the Ktot for this house. Calculate the annual energy used to heat this house (in GJ).

Calculate the overall mass transfer coefficient (1/sec) for an air stripping column removing chloroform (CHCl3) from groundwater. The water flow is 170 gal/min; column diameter = 3.0 ft; the column packing including Rashig rings (25 mm); a liquid diffusivity of 6*10-6 cm2/s; an air-to-water ratio = 100:1.   Compare this value to that is the packing were either Berl saddles (25 mm) or Tile (75 mm).

Question 3.3 When the air with a pressure of 0.1 MPa and a specific volume of 0.8 m³/kg was provided into a compressor at a flow rate of 0.25 kg/s, its pressure became 0.7 MPa and its specific volume became 0.2 m³/kg. Through the compression, the specific internal energy was increased by 80 kJ/kg, and there was heat loss of 50 kJ/s to the environment. In this case, calculate the work [k]/s = kW] that the compressor did in unit time. Potential energy and kinetic energy can be negligible.

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