Energy management and Audit question A steam main 150mm outside diameter containing wet steam at 28 bar is insulated with an inner layer of diatomaceous earth, 40mm thick, and an outer layer of 85% magnesia, 25mm thick. The inside surface of the pipe is at the steam temperature, and the heat transfer coefficient for the outside surface of the lagging is 17 W/m2 K. The thermal conductivities of diatomaceous earth and 85% magnesia are 0.09, and 0.06 W/m K respectively. Neglecting radiation, and the thermal resistance of the pipe water flow rate is 1400 kg/h. Taking the specific heat capacity of water as 4.19 kj/kg K, calculate; The required pipe length for parallel-flow The required pipe length for counter-flow

Energy management and Audit question A steam main 150mm outside diameter containing wet steam at 28 bar is insulated with an inner layer of diatomaceous earth, 40mm thick, and an outer layer of 85% magnesia, 25mm thick. The inside surface of the pipe is at the steam temperature, and the heat transfer coefficient for the outside surface of the lagging is 17 W/m2 K. The thermal conductivities of diatomaceous earth and 85% magnesia are 0.09, and 0.06 W/m K respectively. Neglecting radiation, and the thermal resistance of the pipe water flow rate is 1400 kg/h. Taking the specific heat capacity of water as 4.19 kj/kg K, calculate; The required pipe length for parallel-flow The required pipe length for counter-flow

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter2: Steady Heat Conduction

Section: Chapter Questions

Problem 2.49P

See similar textbooks

Similar questions

Determine the rate of heat transfer per meter length to a light oil flowing through a 2.5-cm-ID, 60-cm-long copper tube at a velocity of 0.03 m/s. The oil enters the tube at 16C, and the tube is heated by steam condensing on its outer surface at atmospheric pressure with a heat transfer coefficient of 11.3 kW/m K. The properties of the oil at various temperatures are listed in the following table: Temperature, T(C) 15 30 40 65 100 (kg/m3) 912 912 896 880 864 c(kJ/kgK) 1.80 1.84 1.925 2.0 2.135 k(W/mK) 0.133 0.133 0.131 0.129 0.128 (kg/ms) 0.089 0.0414 0.023 0.00786 0.0033 Pr 1204 573 338 122 55
3.10 A spherical shell satellite (3-m-OD, 1.25-cm-thick stainless steel walls) re-enters the atmosphere from outer space. If its original temperature is 38°C, the effective average temperature of the atmosphere is 1093°C, and the effective heat transfer coefficient is , estimate the temperature of the shell after reentry, assuming the time of reentry is 10 min and the interior of the shell is evacuated.
2.38 The addition of aluminum fins has been suggested to increase the rate of heat dissipation from one side of an electronic device 1 m wide and 1 m tall. The fins are to be rectangular in cross section, 2.5 cm long and 0.25 cm thick, as shown in the figure. There are to be 100 fins per meter. The convection heat transfer coefficient, both for the wall and the fins, is estimated to be K. With this information determine the percent increase in the rate of heat transfer of the finned wall compared to the bare wall.
Estimate the rate of heat loss per unit length from a 5-cm ID, 6-cm OD steel pipe covered with high-temperature insulation having a thermal conductivity of 0.11 W/(m K) and a thickness of 1.2 cm. Steam flows in the pipe. It has a quality of 99% and is at 150C. The unit thermal resistance at the inner wall is 0.0026(m2K)/W the heat transfer coefficient at the outer surface is 17W/(m2K) and the ambient temperature is 16C.
A domestic refrigerator with inner dimensions of 0,7 m by 0,7 m at the base and height 1m was designed to maintain a set temperature of 6 degrees Celsius. The bodies consist of two 10 mm thick layers of Aluminum (k=225W/mK) separated by a 30 mm polyurethane insulation (k=0,028W/mK). If the average convection heat transfer coefficient at the inner and outer surfaces are 116W/m²K and 14,5W/m²K respectively. Calculate : 1)The individual resistance (R) for each thermal layer, as well as for the refrigerator 2)The steady rate of heat transfer from the interior to maintain the specified temperature in the kitchen at 25 degrees Celsius 3)The outer surface temperature of the Aluminum 4)Sketch the sectional view of the refrigerator showing thermal circuit
A domestic refrigerator with inner dimensions of 0,7 m by 0,7 m at the base and height 1m was designed to maintain a set temperature of 6 degrees Celsius. The bodies consist of two 10 mm thick layers of Aluminum (k=225 W/mK) separated by a 30 mm polyurethane insulation (k=0,028 W/mK). If the convection heat transfer coefficient at the inner and outer surfaces are 11,6 W/m²K and 14,5 W/m²K respectively, calculate the outer surface temperature of Aluminum in degrees Celsius to 2 decimal places. 2)calculate the resistance (R) for the insulation layer in K/W to 4 decimal places. 3)calculate the steady rate of heat transfer from the interior to maintain the specified temperature in the kitchen at 25 degrees Celsius in W to 2 decimal places. 4)calculate the total resistance (R) for the refrigerator in K/W to 4 decimal places
A domestic refrigerator with inner dimensions of 0.7 m by 0.7 m at the base and height 1 m was designed to maintain a set temperature of 6 ˚C. The bodies consist of two 10-mm-thick layers of Aluminium (k = 225 W/mK) separated by a 30 mm polyurethane insulation (k=0.028 W/mK). If the average convection heat transfer coefficient at the inner and outer surfaces are 11.6 W/m2K and 14.5 W/m2K respectively, calculate: the outer surface temperature of the Aluminum in 0C to 2 decimal places
....A journal bearing is to be used for a centrifugal pump where the shaft diameter is 50 mm and the bearing length is 80 mm. The ambient and bearing surface temperatures are 20°C and 45°C, respectively. Which of the following is the heat dissipated by the bearing if the heat dissipation coefficient is 280 W/m2-°C? Group of answer choices 56 W 14 W 73 W 28 W
steam exits the turbine of a steam power plant at 105 F and is to be condensed in a large condenser by cooling water flowing through copper pipes (k = 223 Btu/h-ft-F) of inner diameter 0.5 in. and outer diameter 0.7 in. at an average temperature of 70 F. The heat transfer of vaporization of water at 100F is 1037 Btu/lbm. The heat transfer coefficient are 1500 Btu/h-ft-F on the steam side and 35 Btu/h-ft-F on the water side. Determine the length of the tube required to condense steam at arate of 130 lbm/h.
A domestic refrigerator with inner dimensions of 0.7 m by 0.7 m at the base and height 1 m was designed to maintain a set temperature of 6 ˚C. The bodies consist of two 10-mm-thick layers of Aluminium (k = 225 W/mK) separated by a 30 mm polyurethane insulation (k=0.028 W/mK). If the average convection heat transfer coefficient at the inner and outer surfaces are 11.6 W/m2K and 14.5 W/m2K respectively, calculate: the steady rate of heat transfer from the interior to maintain the specified temperature in the kitchen at 25 ˚C in W to 2 decimal places.
A single-cylinder air-cooled lawn mower engine operates under steady conditions. The cylinder temperature cannot exceed 300 ⁰C. To cool the engine, annular fins are placed around the cylinder. The fins are 0.3 cm thick and are 2 cm long from base to tip. The fins are made of cast iron (k = 52 W/mK). The outside diameter of the engine cylinder at the base of the fin is 0.3 m. Assume that the engine operates in 30 ⁰C air and that the heat transfer coefficient on the sides and tip of the fin is 12 Wm^-2K^-1. Determine the number of fins needed to cool a 3 kW engine to the given temperature if the engine has an efficiency of 30 % and 50 % of the total heat given off by the engine actually is dissipated through the fins ?
A domestic refrigerator with inner dimensions of 0.7 m by 0.7 m at the base and height 1 m was designed to maintain a set temperature of 6 ˚C. The bodies consist of two 10-mm-thick layers of Aluminium (k = 225 W/mK) separated by a 30 mm polyurethane insulation (k=0.028 W/mK). If the average convection heat transfer coefficient at the inner and outer surfaces are 11.6 W/m2K and 14.5 W/m2K respectively, calculate the total resistance(R) for the refrigerator in K/W to 4 decimal places from thermodynamics