3. A pipe carrying the liquid at -20°C is 10 mm in outer diameter and is exposed to ambient at 25°C with convective heat transfer coefficient of 50 W/m²-K. It is proposed to apply the insulation of material having thermal conductivity of 0.5 W/m-K. Calculate the heat loss for 2.5 mm, 7.5 mm and 15 mm thickness of insulation over 1 m length. Which one is more effective thickness of insulation?

3. A pipe carrying the liquid at -20°C is 10 mm in outer diameter and is exposed to ambient at 25°C with convective heat transfer coefficient of 50 W/m²-K. It is proposed to apply the insulation of material having thermal conductivity of 0.5 W/m-K. Calculate the heat loss for 2.5 mm, 7.5 mm and 15 mm thickness of insulation over 1 m length. Which one is more effective thickness of insulation?

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.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.1P: 1.1 On a cold winter day, the outer surface of a 0.2-m-thick concrete wall of a warehouse is exposed...

See similar textbooks

Similar questions

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
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.
2.9 In a large chemical factory, hot gases at 2273 K are cooled by a liquid at 373 K with gas-side and liquid-side convection heat transfer coefficients of 50 and , respectively. The wall that separates the gas and liquid streams is composed of a 2-cm thick oxide layer on the gas side and a 4-cm thick slab of stainless steel on the liquid side. There is a contact resistance between the oxide layer and the steel of . Determine the rate of heat loss from hot gases through the composite wall to the liquid.
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.
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.
2.42 A circumferential fin of rectangular cross section, 3.7-cm OD and 0.3 cm thick, surrounds a 2.5-cm- diameter tube as shown below. The fin is constructed of mild steel. Air blowing over the fin produces a heat transfer coefficient of K. If the temperatures of the base of the fin and the air are and , respectively, calculate the heat transfer rate from the fin.
2.45 Heat is transferred from water to air through a brass wall . The addition of rectangular brass fins, 0.08 cm thick and 2.5 cm long, spaced 1.25 cm apart, is contemplated. Assuming a water-side heat transfer coefficient of and an airside heat transfer coefficient of , compare the gain in heat transfer rate achieved by adding fins to (a) the water side, (b) the air side, and (c) both sides. (Neglect temperature drop through the wall.)
A 15 mm diameter cylindrical nuclear fuel rod is housed in a hollow ceramic cylinder concentric to the rod with an inner diameter of 35 mm and an outer diameter of 110 mm. This creates an air gap between the fuel rod and the hollow ceramic cylinder with a convective heat transfer coefficient of 10 W/m²·K. The hollow ceramic cylinder has a thermal conductivity of 0.07 W/m·K and its outer surface maintains a constant temperature of 30 °C. If the fuel rod generates heat at a rate of 1 MW/m³. Solving, the temperature at the surface of the fuel rod is 1026°C. I need the solution with fundamental concepts (Textically with definitions) of how the heat flow behaves in the system. NOT THE MATHEMATICAL RESOLUTION. I already know how to solve it.
A 15 mm diameter cylindrical nuclear fuel rod is housed in a hollow ceramic cylinder concentric to the rod with an inner diameter of 35 mm and an outer diameter of 110 mm. This creates an air gap between the fuel rod and the hollow ceramic cylinder with a convective heat transfer coefficient of 10 W/m²·K. The hollow ceramic cylinder has a thermal conductivity of 0.07 W/m·K and its outer surface maintains a constant temperature of 30 °C. If the fuel rod generates heat at a rate of 1 MW/m³. Solving, the temperature at the surface of the fuel rod is 1026°C. Explain how the heat flow behaves in the system, using the fundamental concepts.
A 15 mm diameter cylindrical nuclear fuel rod is housed in a hollow ceramic cylinder concentric to the rod with an inner diameter of 35 mm and an outer diameter of 110 mm. This creates an air gap between the fuel rod and the hollow ceramic cylinder with a convective heat transfer coefficient of 10 W/m²·K. The hollow ceramic cylinder has a thermal conductivity of 0.07 W/m·K and its outer surface maintains a constant temperature of 30 °C. If the fuel rod generates heat at a rate of 1 MW/m³. Solving, the temperature at the surface of the fuel rod is 1026°C. Give the solution from fundamental concepts of how the heat flow behaves in the system.
A 15 mm diameter cylindrical nuclear fuel rod is housed in a hollow ceramic cylinder concentric to the rod with an inner diameter of 35 mm and an outer diameter of 110 mm. This creates an air gap between the fuel rod and the hollow ceramic cylinder with a convective heat transfer coefficient of 10 W/m²·K. The hollow ceramic cylinder has a thermal conductivity of 0.07 W/m·K and its outer surface maintains a constant temperature of 30 °C. If the fuel rod generates heat at a rate of 1 MW/m³. Determine the temperature at the surface of the fuel rod. Note: Give the solution from fundamental concepts of how the heat flow behaves in the system
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?