Heating Ventilating and Air Conditioning: Analysis and Design
6th Edition
ISBN: 9780471470151
Author: Faye C. McQuiston, Jeffrey D. Spitler, Jerald D. Parker
Publisher: Wiley, John & Sons, Incorporated
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Chapter 5, Problem 5.23P
A basement is
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6. A 1.5 m pipe of negligible thickness holding a hot fluid at 140°C and having an outer diameter of 0.4 m
is insulated with three layers of each 50 mm thick insulation of k₁ = 0.02; k2 = 0.06; and k3= 0.16 W/m-K
(starting from inside). The outside surface temperature is 30°C. Determine
a. the heat loss in Watts,
b. the temperatures between interfaces of insulating layers in °C
3. A heat generating wall is insulated at the left surface. The right surface is
exposed to air having the temperature (T) of 10°C and the heat transfer
coefficient (h) of 55 W/m2.°C. Twenty-five pin fins with square cross section
are attached to the right surface of the wall. The thickness of the wall (Lw) is
24 cm. The height and the width of the wall are both 50 cm. Each fin has the
thickness (t) of 5 cm and the length (Lt) of 12 cm. Thermal conductivities of
the wall and the fins are kw = 60 W/m.°C and kr= 150 W/m.°C. What is the
volumetric rate of heat generation (egen) if the maximum temperature of the
wall is 200°C?
Air
Insulated
Te, h
Lw
Question 6
A steel pipe (k = 48 W/m-K) of a heating system carries wet steam at 120 °C. The inner and outer
diameters of the pipe are 15 cm and 16 cm respectively. The pipe is insulated on the outside with
rockwool insulation (k = 0.05 W/m K) of thickness 8 cm. The ambient air temperature is 32 °C. The
outside heat transfer coefficient is 20 W/m2-K. The thermal resistance between the inner pipe surface
and the steam is negligible. Calculate the rate of heat flow (in W) from the steam to the ambient over a
5 m length of pipe.
Round your answer to 2 decimal places.
Add your answer
Follow-up question to Question 6, calculate the temperature (in °C) of the outer surface of the
insulation.
Round your answer to 2 decimal places.
Add your answer
Follow-up question to Question 6, calculate the rate of condensation of steam (in kg/hr) over the 5-m
lenzth of pipe if the latent heat of steam is 2200 k/kg.
Rc und your answer to 2 decimal places.
Add your answer
Chapter 5 Solutions
Heating Ventilating and Air Conditioning: Analysis and Design
Ch. 5 - Determine the thermal conductivity of 4 in. (100...Ch. 5 - Compute the unit conductance C for 512 in. (140...Ch. 5 - Compute the unit thermal resistance and the...Ch. 5 - What is the unit thermal resistance for an inside...Ch. 5 - Compute the thermal resistance per unit length for...Ch. 5 - Assuming that the blocks are not filled, compute...Ch. 5 - The partition of Problem 5-4 has still air on one...Ch. 5 - The pipe of Problem has water flowing inside with...Ch. 5 - Compute the overall thermal resistance of a wall...Ch. 5 - Compute the overall heat-transfer coefficient for...
Ch. 5 - Estimate what fraction of the heat transfer for a...Ch. 5 - Make a table similar to Table 5-4a showing...Ch. 5 - Estimate the unit thermal resistance for a...Ch. 5 - Refer to Problem 5-13, and estimate the unit...Ch. 5 - A ceiling space is formed by a large flat roof and...Ch. 5 - A wall is 20 ft (6.1 m) wide and 8 ft (2.4 m) high...Ch. 5 - Estimate the heat-transfer rate per square foot...Ch. 5 - A wall exactly like the one described in Table...Ch. 5 - Prob. 5.19PCh. 5 - Compute the overall heat-transfer coefficient for...Ch. 5 - Compute the overall heat transfer for a single...Ch. 5 - Determine the overall heattransfer coefficient for...Ch. 5 - A basement is 2020ft(66m) and 7 ft (2.13 m) below...Ch. 5 - Estimate the overall heat-transfer coefficient for...Ch. 5 - Rework Problem 5-23 assuming that the walls are...Ch. 5 - A heated building is built on a concrete slab with...Ch. 5 - A basement wall extends 6 ft (1.8 m) below grade...Ch. 5 - A 2440ft(7.312.2m) building has a full basement...Ch. 5 - The floor of the basement described in Problem...Ch. 5 - Assume that the ground temperature tg is 40 F (10...Ch. 5 - Use the temperatures given in Problem 5-30 and...Ch. 5 - A small office building is constructed with a...Ch. 5 - A 100 ft length of buried, uninsulated steel pipe...Ch. 5 - Estimate the heat loss from 100 m of buried...Ch. 5 - A large beverage cooler resembles a small building...Ch. 5 - Consider the wall section shown in Fig. 5-10. (a)...Ch. 5 - A building has floor plan dimensions of 3060ft....Ch. 5 - Compute the temperature of the metal roof deck of...Ch. 5 - Consider the wall section shown in Fig. -4a,...Ch. 5 - Consider the knee space shown in Fig. 5-11. The...Ch. 5 - Estimate the temperature in an unheated basement...
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- 2.30 An electrical heater capable of generating 10,000 W is to be designed. The heating element is to be a stainless steel wire having an electrical resistivity of ohm-centimeter. The operating temperature of the stainless steel is to be no more than 1260°C. The heat transfer coefficient at the outer surface is expected to be no less than in a medium whose maximum temperature is 93°C. A transformer capable of delivering current at 9 and 12 V is available. Determine a suitable size for the wire, the current required, and discuss what effect a reduction in the heat transfer coefficient would have. (Hint: Demonstrate first that the temperature drop between the center and the surface of the wire is independent of the wire diameter, and determine its value.)arrow_forwardA cooling system is to be designed for a food storage warehouse for keeping perishable foods cool prior to transportation to grocery stores. The warehouse has an effective surface area of 1860 m2 exposed to an ambient air temperature of 32C. The warehouse wall insulation (k=0.17W/(mK)) is 7.5 cm thick. Determine the rate at which heat must be removed (W) from the warehouse to maintain the food at 4C.arrow_forward2.45 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.)arrow_forward
- QUESTION 58 A domestic refrigerator with inner dimensions of 0.7 m by 0.7 m at the base and height 1 m was designed to maintain a set temperature of 6 °C. The bodies consist of two 10-mm-thick layers of Aluminium (k 225 W/mK) separated by a 30 mm polyurethane insulation (k=0.028 W/mK). If the average convection heat transfer coefficient at the inner and outer surfaces 11.6 W/m2K and 14.5 W/m2K are respectively, calculate: the outer surface temperature of the Aluminum in °C to 2 decimal places.arrow_forward1. For a steam pipe with a given diameter of 10 cm covered by two (2) layers of insulation. The first insulation has a thickness of 4 cm and a coefficient of thermal conductivity of 0.08 W/m.K. and the second insulation has a thickness of 3 cm and a thermal conductivity of 0.15 W/m.K. The steam main conveys steam at a pressure of 1.70 MPa with 25°C superheat. Outside temperature is 27°C. The pipe is 30 meters in length. (tsat @ 1.70 MPa = 204°C). Determine the following: a) The heat loss in KW b) Explain the concepts/principles that were considered and the factors that affected the condition of the above mentioned items (a & b).arrow_forwardQ2/ A plane wall (K =17 W/m.°C ) with (60 mm) thick. Both sides of the wall are insulated with ( 2 cm) layer of insulating material having (K=0.22 W/m.°C ) The heat transfer coefficient, considering convection on both sides of wall are ( 120 and 10 W/m.°C ) respectively. Calculate the heat transfer per unit area if the temperature difference across the wall is (90 °C).arrow_forward
- 12. A 3.1 cm long straight rectangular fin has a thickness of 2.7 mm. The thermal conductivity is 52 W/m K. The fin is attached to a wall maintained at 190 °C and is exposed to a convection environment at 40 °C and h- 31 W/m2 K. What is the fin efficiency? Express your answer in percent.arrow_forwardQuestion 1.2:Consider heat loss through the two walls of a house on a winter night. The walls are identical, except that one of them has a tightly fit glass window. Through which wall will the house lose more heat? Explain. Question 2.1: What advantage does the effectiveness-NTU method have over the LMTD method?arrow_forwardA 10-m-long, 5-cm-outer-radius cylindrical steam pipe is covered with 3-cm thick cylindrical insulation with a thermal conductivity of 0.05 W/m. °C. If the rate of heat loss from the pipe is 1000 W, what would be the temperature drop (in °C) across the insulation? Select one: O a. 163°C b. 48°C c. 79°C d. 150°C e. 600°Carrow_forward
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