Answer: 1.571 W/m2 K : 32.4 W/m2 : 8.9 ºC - how to reach these 7. (i)(ii)In order to allow the computation of the winter heat loss from abuilding, overall heat transfer coefficients must be evaluated foreach element of the building envelope - walls, glazing, roof.Incorporated into these U-values are inside and outsideradiation heat transfer coefficients, the recommended values ofwhich are 5.7% and 4.6ɛ W/m²K respectively. Verify thesefigures for inside and outside design temperature of 20°C and 0°C. Comment on any assumptions made.The external wall of the Royal College Building consists of 600mm thick sandstone (k = 1.5 W/mK) lined on the inside with 16mm plaster (k = 0.46 W/mK). Taking the inside and outsideconvection heat transfer coefficients as 3.0 and 7.7 W/m²Krespectively, and the surface emissivity value of 0.95,determine:(a) the overall heat transfer coefficient and the design heatloss per unit area(b)the temperature halfway-through the sandstone.

Answered: Image /qna-images/answer/9e8f580c-330f-423e-ba62-ae249c7845dc.jpg

Answered: 7. (i) (ii) In order to allow the…

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.

Chapter8: Natural Convection

Section: Chapter Questions

Problem 8.50P

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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?
(50 marks) Q: A hot surface at 125°C is to be cooled by attaching 4 cm long, 0.2 cm diameter aluminum pin fins (k =237 Wim. °C) to it, with a center-to- center distance of 0.5 cm. The temperature of the surrounding medium is 25 °C, and the heat transfer coefficient on the surfaces is fos cm 25 W/m?. C. Determine the rate of heat transfer from the surface 0.2 for a Ix0.5 m section of the plate. Also, determine the overall effectiveness of the fins.
Heat transfer
A finned surface has been added to cool an electronic part. The surface temperature of the electronic part in contact with the fins is 60 ° C, the convection coefficient between the environment and the finned surface is 40 W / m? .K and the thermal conductivity coefficient for the fin material (aluminum) is 180 W / m.K. a. The amount of Heat (W) per unit time thrown into the environment in case the electronic part has wings or no blades, b. Find out wing effectiveness and efficiency?
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1/ 1 100% + T7 Heat Transfer & Applications Q1. The heat flux through a wood slab 50 mm thick, whose inner and outer surface temperatures are 40 and 20°C respectively has been determined to be 40 W/m2. What is the thermal conductivity of the wood. (0.1 W/ mK) o uindow 5 mm thick are
What is the minimum amount of ice at OPC that must be added to the contents of a can of diet cola (340m) to cool it down from 20.5C to 0C Assume that the specific heat and density of the diet colo are the same as for water and that no heat is gained or lost to the surroundings. The latent heat of fusion of ice à 3353/g Specific Heat of water 4.184 J/gK and Density of water is 1 g/mL
REFERENCE: FROM BOOK - ENGINEERING THERMOFLUIDS, M. MASSOUD
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Requested questions: Q1: A house has a composite wall of wood, fiberglass insula- tion, and plaster board, as indicated in the sketch. On a cold winter day, the convection heat transfer coefficients are h, = 60 W/m K and h, = 30 W/m2 K. The total wall surface area is 350 m'. Glass fiber blanket (28 kg/m'), A Plaster board, - Plywood siding. k, (a) Determine a symbolic expression for the total thermal resistance of the wall, including inside and outside convection effects for the prescribed conditions. Inside Outside A, T20°c T-15°C 111 (b) Determine the total heat loss through the wall. (c) If the wind were blowing violently, raising h, to 300 W/m K, determine the percentage increase in 10 mm 100 mm- - 20 mm the heat loss. Q2: The walls of a refrigerator are typically constructed by sand- wiching a layer of insulation between sheet metal panels. Consider a wall made from fiberglass insulation of thermal conductivity k, = 0.046 W/m K and thickness L, = 50 mm and steel panels. each of…

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