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A wet towel hangs on a clothes line under conditions for which one surface receives solar irradiation of
Determine the temperature
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Fundamentals of Heat and Mass Transfer
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- A summer air conditioning system, consisting of a cooling coil and a reheat coil, supplies air to a space maintained at 25°C db-temperature and 18°C wb-temperature. The sensible and latent heat loads on the space are 15 kW and 10 kW respectively. The conditions of the air leaving the cooling coil are 12°C db-temperature and 90% relative humidity. The pressure is constant at 101.325 kPa. Determine:The db-temperature in °C.The dry air mass flow rate of the air supplied in kg/s.The refrigeration capacity of the cooling coil in kW.The rate of heat input by the reheat coil in kW.The bypass factor of the cooling coil in %.arrow_forward7.Consider a person standing in a room maintained at 20°C at all times. The inner surfaces of the walls, floors, and ceiling of the house are observed to be at an average temperature of 12°C in winter and 23°C in summer. Determine the rates of radiation heat transfer between this person and the surrounding surfaces in both summer and winter if the exposed surface area, emissivity, and the average outer surface temperature of the person are 1.6 m2, 0.95, and 32°C, respectively.arrow_forwardAn air conditioning system, shown schematically below, supplies air at the rate of 4 kg/s to a space maintained at a db-temperature of 27°C and relative humidity of 50%. The sensible and latent heat loads on the space are 46 kW and 20 kW respectively. Outdoor air at 35°C db-temperature and 24°C wb-temperature is introduced at the rate of 1.1 kg/s. The relative humidity of the air leaving the cooling coil is 90%. The pressure is constant at 101.3 kPa. Determine:the supply air temperature in °Cthe supply air relative humidity in %the mass flow rate of the air that bypasses the cooling coil in kg/sthe refrigeration capacity of the cooling coil in kWarrow_forward
- Question 6 A 1000-W iron is left on the ironing board with its base exposed to the air at 23°C. The convection heat transfer coefficient between the base surface and the surrounding air is 35W/m2 ·°C. If the base has an emissivity of 0.9 and a surface area of 0.02 m2 , determine the temperature of the base of the iron (? = 0.6, σ = 5.67 × 10−8 W/?2 ? 4 )arrow_forwardA summer air conditioning system, consisting of a cooling coil and a reheat coil, supplies air to a space maintained at 25°C db-temperature and 20°C wb-temperature. The sensible and latent heat loads on the space are 15 kW and 10 kW respectively. The conditions of the air leaving the cooling coil are 13°C db-temperature and 90% relative humidity. The pressure is constant at 101.3 kPa. Determine:The db-temperature of the supply air in °C.The dry-air mass flow rate of the air supplied in kg/s.The rate of heat input by the reheat coil in kW.The bypass factor of the cooling coil in %.arrow_forwardA summer air conditioning system, consisting of a cooling coil and a reheat coil, supplies air to a space maintained at 25°C db-temperature and 18°C wb-temperature. The sensible and latent heat loads on the space are 15 kW and 10 kW respectively. The conditions of the air leaving the cooling coil are 12°C db-temperature and 90% relative humidity. The pressure is constant at 101.325 kPa. Determine: The dry air mass flow rate of the air supplied in Kg/s The refrigeration capacity of the cooling coil in kW. The rate of heat input by the reheat coil in kW.arrow_forward
- 2. (a) Consider a 25-cm-diameter spherical ball at 700 K suspended in air and assume the emissivity of the ball to be ε=0.95. Calculate: (i) the total emissive power in kW/m2; (ii) the total amount of radiation emitted by the ball in 3 minutes. (b) The inner and outer surfaces of a 25-cm-thick wall are at 27 oC and 45 oC, respectively. The outer surface of the wall exchanges heat by radiation with surrounding surfaces at 40 oC, and convection with ambient air at 42 oC with convection heat transfer coefficient of 9.0 W/m2 K. Solar radiation incident on the surface is at a rate of 150 W/m2. If the emissivity and the solar absorptivity of the outer surface are 0.75 and 0.85, respectively: (i) write the expression of the energy balance at the outer surface;…arrow_forwardA thermocouple used to measure the temperature of hot air flowing in a duct whose walls are maintained at Tw = 500 K shows a temperature reading of Tth = 850 K. Assuming the emissivity of thethermocouple junction to be 0.6 and the convection heat transfer coefficient to be h = 60 W/m*• °C. determine the actual temperature of air.arrow_forwardConsider a room whose door and windows are tightly closed, and whose walls are well-insulated so that heat loss or gain through the walls is negligible.arrow_forward
- 1. In the process of air conditioning in a humidifier, the air at a dry bulb temperature of 20 °C and 25% RH increases its RH to 40%. Determine the amount of moisture added in the humidifier per kg of dry air. = (kg water/kg air). 2. The air has a dry bulb temperature of 34 °C and a wet bulb temperature of 22°C. The liquid is heated in a heater so that the dry bulb temperature increases to 80 °C. Then the air is passed through the corn kernels to dry. The air coming out of the corn kernels is at bulb temperature. dry 55 °C Then this air is passed to the dehumidifier to reduce its RH to 10%. Draw the course of the air change process on a psychrometric diagram. The rate of air flow through the corn kernels and dehumidifier is 4.0 m/s and the cross-sectional diameter of the pile is 0.7 m. a) Determine the amount of water content lost from the pile of corn kernels (in grams of water/second) b) Determine the amount of water content lost from the air when passing through the…arrow_forwardIn a new residential project, you strongly believe thatdouble-paned windows are ‘better’ than single-paned windows.Compare the rate of heat loss between single and double-panedwindows (1.5 m x 1 m) if the thickness of each pane is (th = 0.4 cm)and (k = 0.9 W/m.K). The indoor and outdoor temperatures are 18°C and 2 °C, respectively. Thickness of the air gap between thedouble-paned windows is (th = 1 cm), and (k = 0.022 W/m.K).Image credit: Windowwhirl.arrow_forwardThe top surface of the passenger car of a train moving at a velocity of 115 km/h is 2.8 m wide and 8 m long. The top surface is absorbing solar radiation at a rate of 380 W/m2 and the temperature of the ambient air is 30°C. Assuming the roof of the car to be perfectly insulated and the radiation heat exchange with the surroundings to be small relative to convection, determine the equilibrium temperature of the top surface of the car. The properties of air at 30°C are (Table A-15) k = 0.02588 W/m⋅°C, v = 1.608 × 10−5 m2/s, and Pr = 0.7282.The equilibrium temperature of the top surface of the car is:arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning