Question

1. Double glazing consists of two layers of glass separated by an air gap. Which of the following statements about double glazing is the most correct?

Group of answer choices

A thicker air gap reduces convection and has no significant effect on conduction

A thinner air gap reduces convection and has no significant effect on conduction

A thicker air gap reduces both convection and conduction

A thicker air gap reduces convection but increases conduction

A thinner air gap reduces both convection and conduction

A thinner air gap reduces convection but increases conduction

2.

Hydrogen as an energy source has advantages and disadvantages. Which of the following is an advantage?

Group of answer choices

It is a gas at room temperature, so it is easy to handle and store.

It has a high energy density per unit mass.

It is freely available on the Earth in its molecular form.

It has a high energy density per unit volume.

It is corrosive and flammable.

3.

Use the excel simulation with the default parameters. Keeping everything else constant, increasing the heating power will:

Group of answer choices

Increase the time constant and reduce the daily temperature variation

Increase the time constant and increase the daily temperature variation

Reduce the time constant and reduce the daily temperature variation

Have no effect on the time constant and the daily temperature variation

Reduce the time constant and increase the daily temperature variation

4.

Use the excel simulation, start with the default parameters but set the heating to zero. Keeping everything else constant, changing from double glazed to single glazed will:

Group of answer choices

Have no effect on the inside minimum temperature or the inside maximum temperatures

Increase the inside minimum temperature and reduce the inside maximum temperature

Increase both the inside minimum and maximum temperatures

Reduce both the inside minimum and maximum temperatures

Reduce the inside minimum temperature and increase the inside maximum temperature

Answer 1

1. The air gap is too narrow to allow the air to circulate easily. This therefore reduces the rate of heat transfer by convection. The trapped air reduces the rate of heat loss through the window by conduction and convection.
but, smaller air gap reduces thermal resistivity
hence, A thinner air gap reduces convection but increases conduction

2. From the given options
It is a gas at room temperature, so it is easy to handle and store : this is false, being a gas, hydrogen is difficult to handle
It has a high energy density per unit mass : this is true since hydrogen is a light gas , and highly compresible
It is freely available on the Earth in its molecular form : its false, this is not true
It has a high energy density per unit volume : this is also true as Hydrogen gas has more than 100 times per unit volume energy density
It is corrosive and flammable : is not an advantage
hence

It has a high energy density per unit mass
It has a high energy density per unit volume

3. Increasing the heating power will have no effect on the time constant which is dependent on the material properties of the room
moreover, the temeprature variations will remain the same as well , only relative temerature variations will reduce, absolute temeprature variations remain same
hence Have no effect on the time constant and the daily temperature variation

4. Keeping everything else constant, changing from double glazed to single glazed will:
reduce the thermal resistance
hence more power loss will be there from the room
hence, Reduce both the inside minimum and maximum temperatures