Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

11.43.Compare heat-transfer rates through layers of human

skin, human muscle, and human fat tissue. Assume a

5-mm thickness and a temperature difference of 2 °C

across each layer.

11.44. Calculate the heat-transfer rate through a 24 ft

2

door

with. The indoor and outdoor tem-

peratures are 68 °F and 10 °F.

11.45. Look up the low- and high-daily-temperature values

for the month of October 2009 for your town and cal-

culate the degree days for the given month.

11.46.For your town calculate the degree-days for the months

of December, January, and February 2009 and com-

pare it to the 2009 annual degree-days value.

11.47. For a building located in Baltimore, Maryland with

annual heating degree-days (dd) of 4654, a heating load

(heat loss) of 30,000 Btu /h, and a design temperature

difference of 52°F (68°F indoor and 16°F outdoor),

estimate the annual energy consumption. If the build-

ing is heated with a furnace with an efficiency of 92%,

how much gas is burned to keep the home at 68°F?

State your assumptions.

11.48.For a building located in Boston, Massachusetts with

annual heating degree-days (dd) of 5634, a heating load

(heat loss) of 42,000 Btu /h, and a design temperature

difference of 62°F (68°F indoor and 6°F outdoor), esti-

mate the annual energy consumption. If the building is

heated with a furnace with an efficiency of 98%, how

much gas is burned to keep the home at 68°F? State

your assumptions.

11.49. For a building located in Detroit, Michigan with

annual heating degree-days (dd) of 6232, a heating load

(heat loss) of 52,000 Btu /h, and a design temperature

difference of 73°F (68°F indoor and 5°F outdoor),

estimate the annual energy consumption. If the build-

ing is heated with a furnace with an efficiency of 92%,

how much gas is burned to keep the home at 68°F.

State your assumptions.

U0.73

Btu

h#ft^2 #°F

11.50.Visit the National Fenestration Rating Council

(NFRC) website at http://www.nfrc.org and lookup the

definition of energy performance ratings given by

Athrough E. Write a brief report discussing your

findings.

A. U-Factor

B. Solar Heat Gain Coefficient (SHGC)

C. Visible Transmittance (VT)

D. Air Leakage

E. Condensation Resistance

Problems 343

Problem 11.50

Source: Courtesy of The National Fenestration Rating Council (NFRC).

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