A pipe is used to transport refrigerant R-134a with an inner radius of 0.03m, outer radius of 5 cm, and thermal conductivity of k=2.5 W/m-K. The inner and outer surfaces of the pipe are maintained at an average temperature of 20°C and 40°C, respectively. Obtain a general relation for the temperature distribution inside the pipe under steady conditions. Determine the rate of heat gain per unit length by the refrigerant through the pipe.

A pipe is used to transport refrigerant R-134a with an inner radius of 0.03m, outer radius of 5 cm, and thermal conductivity of k=2.5 W/m-K. The inner and outer surfaces of the pipe are maintained at an average temperature of 20°C and 40°C, respectively. Obtain a general relation for the temperature distribution inside the pipe under steady conditions. Determine the rate of heat gain per unit length by the refrigerant through the pipe.

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.

Chapter3: Transient Heat Conduction

Section: Chapter Questions

Problem 3.16P: 3.16 A large, 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer...

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3.16 A large, 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer coefficient on one side is and on the other side is . If the temperature of both streams is suddenly changed from 38°C to 93°C, determine how long it takes for the copper plate to reach a temperature of 82°C.
In a thermal power plant, a horizontal copper pipe of "D" diameter, "L" length and thickness 1.7 cm enters into the boiler that has the thermal conductivity as 0.3 W/mK. The boiler is maintained at 107degreeC and temperature of the water that flows inside the pipe is at 31degreeC. If the energy transfer (Q) is 124925 kJ in 7 hours. Determine the Heat transfer rate, Surface area of the pipe and Diameter & Length of the pipe, if D = 0.012 L.Change in Temperature (in K) Heat Transfer Rate (in W) Surface Area of the Pipe (m2) Pipe Length (in m) Pipe Diameter (in mm)
QUESTION 3: Warm air is blown over the inner surface of the windshield of an automobile to defrost ice accumulated on the outer surface. The windshield has a thickness of 5 mm and thermal conductivity of 1.4 W/m-K. The outside ambient temperature is -10°C and the convection heat transfer coefficient is 200 W/m²-K, while the ambient temperature inside the automobile is 25°C. Determine the value of the convection heat transfer coefficient for the warm air blowing over the inner surface of the windshield necessary to cause the accumulated ice to begin melting.
.A 3-mm diameter and 5-mlong electric wire is tightly wrapped with a 2-mm thick plastic Cover whose thermal conductivity of k=0.15W/m°C. Électrical measurements indicate that the aurrent of 10A passes through the wire and there is a voltage drop of 8V alorg the wire. If the insulated wire is exposed to a medium at T„=30°C with a heat transfer coefficient of l=12W/n?.°C, detemine the temperature at the interface of the wire and the plastic cover under steady operation. Also determine whether doubling the thickness of the plastic cover will increase ar decrease this interface temperature. Your solution must state goveming equations and associated assumptions, illustration and step by step execution of the overall solution." Supporting Equations 280K
A cold storage wall, whose components and dimensions are given below, is formed by connecting layers A, B, C, D, E and F in series and in parallel. The temperature of the outside air is 30 oC and the temperature of the inside of the warehouse is -4 oC. If the film heat transfer coefficient between the air in the warehouse and the E layer is 24 W/m2 oC and the film heat transfer coefficient between the outer surface of the flat wall (A and F layers surface) and the atmospheric air is 16 W/m2 oC; Calculate the heat transferred in a day. (KA= 0.17 W/m.K, kc 0.98 W/m.K) (kD= 0.21 W/m.K, KF= 0.58 W/m.K) XA=3cm B KBK= 0.024 W/m.K, KE=0.01 W/m.K, F C D E XB=14 cm Xc=Xp=8cm XE=10cm AF AC AD= A/3 h= 2 m 70 cm
Consider a large plane wall of thickness L = 0.3 m, thermal conductivity k = 2.5 W/m·K, and surface area A = 12 m2. The left side of the wall at x = 0 is subjected to a net heat flux of , while the temperature at that surface is measured to be T1 = 80°C. Assuming constant thermal conductivity and no heat generation in the wall, (a) express the differential equation and the boundary conditions for steady one-dimensional heat conduction through the wall, (b) obtain a relation for the variation of temperature in the wall by solving the differential equation, and (c) evaluate the temperature of the right surface of the wall at x = L.
A 0.5-ampere current is flowing through a long electrically conducting cylindrical rod. The diameter of the rod is 6 mm, the electrical resistance of the rod is R = 2000 /m, and k =0.9 W/m K for the rod. The rod is encased in a 2-mm thick Pyrex tube and a 20°C liquid is flowing over the outer surface of the Pyrex tube. The convection heat transfer coefficient for the liquid h= 800 W/m2 . K. The interfacial conductance (contact resistance) at the interface between the rod and the Pyrex tube is h = 1200 W/m² - K. a) Compute the rate of heat generation in the rod and use it compute the volumetric rate of heat generation. b) Find the temperature drop across the interface between the outer surface of the rod and the inner surface of the Pyrex tube. c) Find the temperature at the center of the rod.
For a metal plate (k = 50 W / m°C and a = 0.000030 m^2 / s) that is at a uniform initial temperature of 90 °C, and which is exposed to a current of air at 20°C with a heat transfer coefficient of 210 W/ m2°C on the surface, determine the temperature at the surface and at a depth of 10 cm after 3 minutes of exposure. Assume a semi-infinite surface, one- dimensional conduction, and constant thermophysical properties
10 m long pipe is being used to deliver steam through a processing plant. The inner radius of the pipe is ri = 6 cm and the thickness of the pipe is 2 cm. Thermal conductivity k = 8 W/m-K and the average temperature steam flowing through the pipe is 160°C, the average convection heat transfer coefficient on the inner surface is given to be h = 20 W/m2-K. If the average temperature on the outer surfaces of the pipe is T2 = 70°C, (a) express the differential equation and the boundary conditions for steady operating conditions, (b) determine a relation for the variation of temperature in the pipe, and (c) evaluate the rate of heat loss (heat of conduction) from the steam through the pipe.
Warm air is blown over the inner surface of the windshield of an automobile to defrost ice accumulated on the outer surface. The windshield has a thickness of 5 mm and thermal conductivity of 1.4 W/m-K. The outside ambient temperature is -10°C and the convection heat transfer coefficient is 200 W/m2-K, while the ambient temperature inside the automobile is 25°C. Determine the value of the convection heat transfer coefficient for the warm air blowing over the inner surface of the windshield necessary to cause the accumulated ice to begin melting.
Consider a wall made of Material A that is 4.5m long, 3.0m high, and 0.22m thick. The interior and exterior design temperatures are Too1 and Too2, respectively, the heat transfer coefficients on the interior and exterior surfaces are 10 and 20W / m2 •C. If insulating material is placed on the inside surface of the wall to maintain the temperature shallow from it to T1. Determine the required thickness of the insulating material.
The temperature at the inner and outer surfaces of a boiler wall made of 25 mm thick steel and covered with an insulating material of10 mm thickness are 300 C and 50C respectively. If the thermal conductivities of steel and insulating material are 58W/mC and 0.116W/mC respectively, determine the total resistance through the boiler wall. (Note area of sample boiler wall is 8 m2)