2. The non-insulated wall thickness is a thin 120 mm diameter water pipe, the outer surface temperature is -15 °C in winter outdoor conditions and a concentric cylindrical ice layer (k=1.94 W/mK) forms on its inner surface. a) If the convection heat transfer coefficient (h) between 3 °C water and 0 °C ice is taken as follow, what is the thickness of the ice layer? b) Flow cuts off, what happens if h0 falls? Your comments? -15 °C Take the convection heat transfer coefficient as the sum of the last two digits ice

2. The non-insulated wall thickness is a thin 120 mm diameter water pipe, the outer surface temperature is -15 °C in winter outdoor conditions and a concentric cylindrical ice layer (k=1.94 W/mK) forms on its inner surface. a) If the convection heat transfer coefficient (h) between 3 °C water and 0 °C ice is taken as follow, what is the thickness of the ice layer? b) Flow cuts off, what happens if h0 falls? Your comments? -15 °C Take the convection heat transfer coefficient as the sum of the last two digits ice

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

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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.)
2.15 Suppose that a pipe carrying a hot fluid with an external temperature of and outer radius is to be insulated with an insulation material of thermal conductivity k and outer radius . Show that if the convection heat transfer coefficient on the outside of the insulation is and the environmental temperature is , the addition of insulation actually increases the rate of heat loss if , and the maximum heat loss occurs when . This radius, is often called the critical radius.
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.
One end of a 0.3-m-long steel rod is connected to a wall at 204C. The other end is connected to a wall that is maintained at 93C. Air is blown across the rod so that a heat transfer coefficient of 17W/m2 K is maintained over the entire surface. If the diameter of the rod is 5 cm and the temperature of the air is 38C, what is the net rate of heat loss to the air?
QUESTION-) 236 °C steam flows in a pipe which features are given below. Inner and outer diameters of pipe are 300 mm and 320 mm. Coefficient of heat transmission is 40 W/mK. It's external ambient is air and it's temperature is 20 °C. Take the temperature of the pipe's external surface 180 °C. It is known that the internal temp convection coefficient is 600 W/m^2K and external heat transfer coefficient is 5,9109 W/m^2K The pipe's length is 500 meter. You need to add the radiation in the calculation. The rate of the radiation emissivity is 0.85. You can take the environmental surface temp directly. Please calculate the heat loss of pipe.
QUESTION-) 236 °C steam flows in a pipe which features are given below. Inner and outer diameters of pipe are 300 mm and 320 mm. Coefficient of heat transmission is 40 W/mK. It's external ambient is air and it's temperature is 20 °C. Take the temperature of the pipe's external surface 180 °C. It is known that the internal temp convection coefficient is 600 W/m^2K and external heat transfer coefficient is 5,9109 W/m^2K The pipe's length is 500 meter. You need to add the radiation in the calculation. The rate of the radiation emissivity is 0.85. You can take the environmental surface temp directly. a-) Please draw this question on the resistance network. b-) Please calculate the heat loss of pipe. c-) By applying insulation to this pipe, it is desired to reduce the heat loss to 20% of the uninsulated loss (option a). Calculate the insulation thickness accordingly. Take glass wool as insulation material.(Conductivity of glass wool = 0.040 W/mK.) Given, The temperature of steam inside the…
QUESTION-) 236 °C steam flows in a pipe which features are given below. Inner and outer diameters of pipe are 300 mm and 320 mm. Coefficient of heat transmission is 40 W/mK. It's external ambient is air and it's temperature is 20 °C. Take the temperature of the pipe's external surface 180 °C. It is known that the internal temp convection coefficient is 600 W/m^2K and external heat transfer coefficient is 5.9109 W/m^2K The pipe's length is 500 meter. You need to add the radiation in the calculation. The rate of the radiation emissivity is 0.85. You can take the environmental surface temp directly. IMPORTANT NOTE: Hi. I sent this question to be solved 3 times. But I faced with different and wrong answers in all. What i want to ask is that doesn't all the resistances except conduction and convection resistances need to change after adding the insulation materials to the pipe? In the solution the people who solved this question took the external surface temp constant. Shouldn't the…
Question 4: Water flows on the inside of a steel pipe with an ID of 2.5 cm. The wall thickness is 2 mm, and the convection coefficient on the inside is 500 W/m2◦C. The convection coefficient on the outside is 12 W/m2 ◦C. Calculate the overall heat-transfer coefficient.
10 cm thick and 1 m wide long when a steel plate is at temperature Ti = 240 ° C, T0 = 40 ° C It is immersed in the hot oil bath. With sheet Heat transfer coefficient between oil h = 600 W / m2K and p = 7833 kg / m3 for steel , cp = 465 J / kgK, k = 43 W / mK, α = 1.2x10-5 m2 / s. a)How much the core temperature of the steel plate after time becomes 100 ° C ? b)What is the temperature inside 3 cm from the surface of the steel plate? c)Within this period, per unit length plate what will be the amount of heat that passes?
A modern cabin has a concrete floor that is 4.50 inches thick. Aroaring fire keeps the interior of the cabin at 21.0 0C while the airtemperature below the cabin is a chilly 2.00 0C. How much heat(J) is lost through the concrete floor in 4 hrs if the cabin measures4.50 m by 6.50m to 3 sig fig?
(a) If the insulation is 27.5 mm thick and its inner and outer surfaces are maintained at Ts,1=800 K and Ts,2=490 K, respectively, what is the rate of heat loss per unit length (q′) of the pipe, in W/m?(b) Determine the rate of heat loss per unit length (q′), in W/m, and outer surface temperature Ts,2, in K, for the steam pipe with the inner surface temperature fixed at Ts,1=800 K, inner radius r1=0.06 m, and outer radius r2= 0.18 m. The outer surface is exposed to an airflow (∞T∞=25°C) that maintains a convection coefficient of h=25 W/m2·K and to large surroundings for which Tsur= T∞=25°C. The surface emissivity of calcium silicate is approximately 0.8.
A vertical cylinder 6 ft tall and 1 ft in diameter might be used to approximate a man for heat-transfer purposes. Suppose the surface temperature of the cylinder is 78°F, h=2 Btu/h · ft2 . °F, the surface emissivity is 0.9, and the cylinder is placed in a large room where the air temperature is 68°F and the wall temperature is 45°F. Calculate the heat lost from the cylinder. Repeat for a wall temperature of 80°F. What do you conclude from these calculations? Known, Find, Schematic Diagram, Assumption, Properties, Analysis and Comments