Question 6 A steel pipe (k = 48 W/m-K) of a heating system carries wet steam at 120 °C. The inner and outer diameters of the pipe are 15 cm and 16 cm respectively. The pipe is insulated on the outside with rockwool insulation (k = 0.05 W/m-K) of thickness 8 cm. The ambient air temperature is 32 °C. The outside heat transfer coefficient is 20 W/m2-K. The thermal resistance between the inner pipe surface and the steam is negligible. Calculate the rate of heat flow (in W) from the steam to the ambient over a 5 m length of pipe. Round your answer to 2 decimal places. Add your answer Follow-up question to Question 6, calculate the temperature (in °C) of the outer surface of the insulation. Round your answer to 2 decimal places. Add your answer Follow-up question to Question 6, calculate the rate of condensation of steam (in kg/hr) over the 5-m length of pipe if the latent heat of steam is 2200 kJ/kg. Rc und your answer to 2 decimal places. Add your answer

Question 6 A steel pipe (k = 48 W/m-K) of a heating system carries wet steam at 120 °C. The inner and outer diameters of the pipe are 15 cm and 16 cm respectively. The pipe is insulated on the outside with rockwool insulation (k = 0.05 W/m-K) of thickness 8 cm. The ambient air temperature is 32 °C. The outside heat transfer coefficient is 20 W/m2-K. The thermal resistance between the inner pipe surface and the steam is negligible. Calculate the rate of heat flow (in W) from the steam to the ambient over a 5 m length of pipe. Round your answer to 2 decimal places. Add your answer Follow-up question to Question 6, calculate the temperature (in °C) of the outer surface of the insulation. Round your answer to 2 decimal places. Add your answer Follow-up question to Question 6, calculate the rate of condensation of steam (in kg/hr) over the 5-m length of pipe if the latent heat of steam is 2200 kJ/kg. Rc und your answer to 2 decimal places. Add your answer

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 2.30P: 2.30 An electrical heater capable of generating 10,000 W is to be designed. The heating element is...

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1.1 On a cold winter day, the outer surface of a 0.2-m-thick concrete wall of a warehouse is exposed to temperature of –5°C, while the inner surface is kept at 20°C. The thermal conductivity of the concrete is 1.2 W/m K. Determine the heat loss through the wall, which is 10-m long and 3-m high. Problem 1.1
1.10 A heat flux meter at the outer (cold) wall of a concrete building indicates that the heat loss through a wall of 10-cm thickness is . If a thermocouple at the inner surface of the wall indicates a temperature of 22°C while another at the outer surface shows 6°C, calculate the thermal conductivity of the concrete and compare your result with the value in Appendix 2, Table 11.
1.4 To measure thermal conductivity, two similar 1-cm-thick specimens are placed in the apparatus shown in the accompanying sketch. Electric current is supplied to the guard heater, and a wattmeter shows that the power dissipation is 10 W. Thermocouples attached to the warmer and to the cooler surfaces show temperatures of 322 and 300 K, respectively. Calculate the thermal conductivity of the material at the mean temperature in W/m K. Problem 1.4
2.30 An electrical heater capable of generating 10,000 W is to be designed. The heating element is to be a stainless steel wire having an electrical resistivity of ohm-centimeter. The operating temperature of the stainless steel is to be no more than 1260°C. The heat transfer coefficient at the outer surface is expected to be no less than in a medium whose maximum temperature is 93°C. A transformer capable of delivering current at 9 and 12 V is available. Determine a suitable size for the wire, the current required, and discuss what effect a reduction in the heat transfer coefficient would have. (Hint: Demonstrate first that the temperature drop between the center and the surface of the wire is independent of the wire diameter, and determine its value.)
An electronic device that internally generates 600 mW of heat has a maximum permissible operating temperature of 70C. It is to be cooled in 25C air by attaching aluminum fins with a total surface area of 12cm2. The convection heat transfer coefficient between the fins and the air is 20W/m2K. Estimate the operating temperature when the fins are attached in such a way that (a) there is a contact resistance of approximately 50 K/W between the surface of the device and the fin array and (b) there is no contact resistance (in this case, the construction of the device is more expensive). Comment on the design options.
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 thick-walled tube of stainless steel with thermal conductivity k=19 W/m°C has inner diameter of 10 cm and outer diameter of 30 cm covered with 5 cm layer of asbestos insulation with thermal conductivity k= 0.2 W/m°C. If the inside of the pipe and outside of insulator temperature is maintained at 600°C and 107°C respectively. Determine the heat loss per meter length of pipe and the tube-insulation interface temperature.
Calculate the heat loss in a pipe 109.7 mm inside diameter and 13.7 m length covered with a layer of 5.9 cm thick of insulation having a thermal conductivity of 0.05 W/m-K. If the temperature of the pipe is 390˚C and the ambient temperature is 38˚C. Answer: 2074.5501 W
Consider a closed cylindrical reactor vessel of diameter D= 1 ft, and length L= 1.5 ft. The surface temperature of the vessel, T1, and the surrounding temperature, T2, are 390 deg. F and 50 deg. F, respectively. The convective heat transfer coefficient, h, between the vessel wall and surrounding fluid is 4.0 Btu/h . ft . ⁰F. Calculate the thermal resistance in ⁰F .h/Btu.
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 cast iron pipe is used to transfer steam with an inlet temperature of 350 C. Inner radius of the pipe is 5 cm. The thickness of the pipe (k=20 W/(mK)) is 0.5 cm and there is an insulation (k=0.07 W/mK) over the pipe with a thickness of 4 cm. Environmental temperature is -5 C. Determine the steady heat loss from the pipe if the steam convection coefficient is 70 W/(m^2K) and environment convection coefficient is 20 W/(m^2K)? Is insulation thickness enough? a)167 W, yes b)187 W, yes c)147 W, yes d)120 W, no e)none
A cast iron pipe is used to transfer steam with an inlet temperature of 300 C. Inner radius of the pipe is 15 cm. The thickness of the pipe (k=25 W/(mK)) is 0.7 cm and there is an insulation (k=0.05 W/mK) over the pipe with a thickness of 5 cm. Environmental temperature is -8 C. Determine the steady heat loss from the pipe if the steam convection coefficient is 80 W/(m^2K) and environment convection coefficient is 25 W/(m^2K)? Is insulation thickness enough? a)197 W, yesb)207 W, yesc)147 W, yesd)150 W, noe)none