When room temperature is kept at 66°F, a 3000 ft2 House without insulation in Morgantown loses in average 4000 BTU/min thermal energy to ambient air during winter time (from November 1st to March 31). The cost of a low efficiency (90) furnace fueled by natural gas is $2000. The cost of a high efficiency (99.5%) furnace fueled by natural gas is $3000. Both furnaces have a life expectation of 20 years. The installation of an insulation layer is estimated to reduce the heat loss by 80% at a cost of $30,000. You can assume the house and insulation layer can be used for 80 years.

(1) Please find the best design for this house for the estimated natural gas price of $3.0/MBTU (current price) and $12.0/MBTU (natural gas price a few years ago), respectively.

(2) Please comments if the application of the heat transfer knowledge helps to reduce the emissions of greenhouse gases.

(3) Check if the methane in natural gas should be considered as greenhouse gas, comments its greenhouse gas potential, and explain the benefit of high efficiency furnace in heating a house.

2) The application of heat transfer knowledge is expressed in the reduction of fuel from year to year. and these decreases in fuel, leads to a decrease in the emissions of greenhouse gases

3) Methane should be considered a greenhouse gas, methane is part of the gases emitted when fuel is burnt hence using a thermally insulated house with a high efficient furnace to reduce the amount of fuel burnt is beneficial in the reduction of the emission of greenhouse gases like methane

Explanation:

Given Data :

Number of days = 150 days ( 1st Nov to 31st March )

Total working time = 150 * 60 *24 = 216000 mins

Heat loss without insulation = 864 Btu/min ( 4000 * 216000 )

heat loss with insulation = ( 1- 0.8 ) * 864 = 172.8 MBTU

1) Best design to use

i) Without insulation, Low efficiency furnace

fuel required = 864 / 0.9 = 960 MBTU

cost of fuel at current price = 3 * 960 = $2880

cost of fuel at old price = $11520

ii) with insulation, low efficiency furnace

fuel required = 172.8 / 0.9 = 192 MBTU,

cost of fuel at current price = $576

cost of fuel at old price = $ 2304

After repeating the same process for every combination it is discovered that the design with the least cost is the use of thermal insulation with a high efficiency furnace Hence it is the best design to implement

2) The application of heat transfer knowledge is expressed in the reduction of fuel from 960MBTU per year to 173.67 MBTU per year. and the decrease in fuel leads to a decrease in the emissions of greenhouse gases

3) Methane should be considered a greenhouse gas, methane is part of the gases emitted when fuel is burnt hence using a thermally insulated house with a high efficient furnace to reduce the amount of fuel burnt is beneficial in the reduction of the emission of greenhouse gases like methane