The interior lighting of refrigerators is provided by incandescent lamps whose switches are actuated by the opening of the refrigerator door. Consider a refrigerator whose 50 W lightbulb remains on continuously as a result of a malfunction of the switch. Assume that the refrigerator is opened 35 times a day for an average of 15 s. If the refrigerator has a COP of 1.3 and the cost of electricity is 8.75 pesos per kWh, determine the increase in the energy consumption of the refrigerator and its cost per year if the switch is not fixed.

please show how to derive h using nusselt equation and solve for qheatloss

A heat pump is required for a single-family 2-story, 3-person, 30 ft x 30 ft x 18 ft (L x W x H), energy- efficient residential house in Philadelphia, PA, for a typical winter season. Assuming a comfortable indoor temperature is 70 °F and on a cold winter day the outdoor temperature is 10 °F. Exercise #1: Calculate total heat loss from a house in Philadelphia on a cold winter day. Assume 40% of the wall area is windows with U-value of 0.81 BTU/hr-ft²-°F. The remaining 60% of the walls has a U-value of 0.2 BTU/hr-ft²-°F. The roof has a U value of 0.05 BTU/hr-ft?-°F and the floor U-value is 0.41 BTU/hr-ft²-°F. For simplicity assume that the ground temperature is the same as the air temperature. [However, in your project design calculations you should refine this assumption.] Assume 0.5 air changes per hour (ACH) due to natural ventilation, such as leakage through windows, etc. Neglect any radiative heat loss/grain from the house. Exercise #2: Determine the watts of electricity needed by…

2 A wire of diameter D = 2 mm and uniform temperature T has an electrical resistance of 0.01 N/m and a current flow of 20 A. (a) What is the rate at which heat is dissipated per unit length of wire? What is the heat dissipation per unit volume within the wire? (b) If the wire is not insulated and is in ambient air and large surroundings for which T = Tsur = 20°C, what is the temperature T of the wire? The wire has an emissivity of 0.3, and the coefficient associated with heat transfer by natural convection may be approximated by an expression of the form, h = C[(T-T)/D]¹/4, where C = 1.25 W/m7/4.K5/4 (c) If the wire is coated with plastic insulation of 2-mm thickness and a thermal conductivity of 0.25 W/m.K, what are the inner and outer surface temperatures of the insulation? The insulation has an emissivity of 0.9, and the convection coefficient is given by the expression of part (b). Explore the effect of the insu- lation thickness on the surface temperatures. Note: 1. The metal wire…

B) A mercury thermometer having a time constant of (90 sec) is initially at (300°C). It is immersed in a bath maintained at (130°C) at t = 0. Determine the temperature reading at (t=3 min) and (t = 5 min).

10.33 Saturated steam at 0.2 bar condenses with a convec- tion coefficient of 6000 W/m²2 · K on the outside of a brass tube having inner and outer diameters of 16 and 19 mm, respectively. The convection coefficient for water flowing inside the tube is 5000 W/m². K. Esti- mate the steam condensation rate per unit length of the tube when the mean water temperature is 30°C.

If solar radiation intensity is 700 W/m² in NJ, how much solar energy arrives at a solar collector with an area of 2 m² in 12 hours? If the solar collector can convert 33% of solar energy collected to electricity, how much electricity (kWh) will be generated?