2. An 18-cm-long, 16-cm-wide, and 12-cm-high metal block (p = 8000 kg/m', c, = 400 J/kg C, k=200 W/mK) initially at 20 "C is placed in an oven at 600 °C for heat treatment. The heat transfer coefficient on the surface of the block is 40 W/m2 "C. How long time is required for the iron block to reach a temperature of 400 °C? 1321 35°C Güneş 1437 2021

2. An 18-cm-long, 16-cm-wide, and 12-cm-high metal block (p = 8000 kg/m', c, = 400 J/kg C, k=200 W/mK) initially at 20 "C is placed in an oven at 600 °C for heat treatment. The heat transfer coefficient on the surface of the block is 40 W/m2 "C. How long time is required for the iron block to reach a temperature of 400 °C? 1321 35°C Güneş 1437 2021

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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3.10 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.
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.
2.55 A long, 1-cm-diameter electric copper cable is embedded in the center of a 25-cm-square concrete block. If the outside temperature of the concrete is 25oC and the rate of electrical energy dissipation in the cable is 150 W per meter length, determine temperatures at the outer surface and at the center of the cable.
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.
NUMBER 3 A food product with 80% moisture content in a 7 cm diameter can wants to be frozen. The density of the product is 1000 kg / m³, the thermal conductivity is 1.0 W / (m K), and the initial freezing temperature is -2.25 ° C. After 8 hours in the freezing medium -35 ° C, the product temperature becomes -10 ° C. Estimate the convection heat transfer coefficient of the freezing medium. Assume the can as an infinite cylinder. h = W / (m² K).
3. A food product with 73% moisture content in a 10 cm diameter can wants to be frozen. The density of the product is 970 kg / m³, the thermal conductivity is 1.2 W / (m K), and the initial freezing temperature is -2 ° C. After 14 hours in the freezing medium -30 ° C, the product temperature becomes -10 ° C. Estimate the convection heat transfer coefficient of the freezing medium. Assume the can as an infinite cylinder. h = Answer W / (m² K).
Number 3 A food product with 80% moisture content in a 7 cm diameter can wants to be frozen. The density of the product is 1000 kg/m³, the thermal conductivity is 1.0 W/(m²K), and the initial freezing temperature is -1.75°C. After 8 hours in the freezing medium -25°C, the product temperature becomes -10°C. Estimate the convection heat transfer coefficient of the freezing medium. Assume the can as an infinite cylinder. h= answer in W/(m²K)
A food product with 73% moisture content in a 10 cm diameter can wants to be frozen. The density of the product is 970 kg / m³, the thermal conductivity is 1.2 W / (m K), and the initial freezing temperature is -2.25 ° C. After 15 hours in the freezing medium -35 ° C, the product temperature becomes -10 ° C. Estimate the convection heat transfer coefficient of the freezing medium. Assume the can as an infinite cylinder. h = .... W / (m² K).
Number 3A food product with 73% moisture content in a 7 cm diameter can wants to be frozen. The density of the product is 970 kg/m³, the thermal conductivity is 1.2W/(m K), and the initial freezing temperature is -2.5°C. After 11 hours in the freezing medium -40°C, the product temperature becomes -10°C. Estimate the convection heat transfer coefficient of the freezing medium. Assume the can as an infinite cylinder. h= answer in W/(m²K)
Water at 5°C is being used to cool apples from an initial temperature of 25° to 10°C. Thewater flow over the surface of the apple creates a convective heat-transfer coefficientof 15 W/(m2-K). Assume the apple can be described as a sphere with a 10 cm diameterand the geometric center is to be reduced to 10°C. The apple properties include thermalconductivity of 0.45 W/(m-K), specific heat of 3.950 kJ/(kg-K), and density of 940 kg/m3.a. Determine the time that the apples must be exposed to the water.b. If the apple is submerged only for 2 hours, what will be its center temperature?
A 4 m thick steel plate initially at 225 °C. Suddenly, both surfaces are exposed to an ambient at 25 °C with a heat transfer coefficient h = 500 W/m2K.What is the temperature at depth 1 cm from the surface at t = 2 minutes after the start of the cooling? For steel: k = 20 W/mK, α = 16x10-6 m2/s.
Question 1:A glass window of width W = 1 m and height H = 2 m is 5 mm thick and has a thermal conductivity of kg=1.4 W/m.K. If the inner and outer surface temperatures of the glass are 15oC and -20oC, respectively, ona cold winter day, what is the rate of heat loss throughthe glass? To reduce heat loss through windows, it iscustomary to use a double pane construction in whichadjoining panes are separated by an air space. If thespacing is 10 mm and the glass surfaces in contact withthe air have temperatures of (last two digit of your Registration number) oC and -15oC, what isthe rate of heat loss from a 1 m x 2 m window? Thethermal conductivity of air is ka=0.024 W/m.K.