1. Final Project - Mechanical

Question 1

Describe types of energy transfer (3)

Answer 1

1. Conduction: energy stransferred by direct contact, Flows from warmer to colder object, Until temp is equal
2. Convection: Gases & liquids, Movement of particles in same direction, Occurs because difference in density
3. Radiation: Energy transferred by electromagnetic waves such as light, microwaves, infrared

Question 2

In the following list, which comfort parameters are provided to the occupants by mechanical systems?

1. Air circulation
2. Thermal equilibrium between the interior and the exterior
3. Relative humidity
4. Barometric pressure
5. Ambient temperature

A) 1, 2, 4
B) 1, 2, 5
C) 1, 3, 5
D) 2, 3, 4
E) 3, 4, 5

Answer 2

C) 1, 3, 5

Question 3

Radiant heat cannot provide _______ to the space and it cannot _____ _____.

For these reasons, radiant heating should be supplemented.

Answer 3

Radiant heat cannot provide ventilation to the space and it cannot react quickly. For these reasons, radiant heating should be supplemented.

Question 4

Describe Heat Loss and Heat Gain.

Answer 4

Heat Loss

• heat loss to exterior in cold weather
• convection / radiation / conduction

Heat Gain

• heat gained within the building
• latent heat / lighting / occupants

Question 5

Describe a radiator and a fin-tube convector.

Answer 5

Radiator

• series /coil of pipes w steam or hot water inside
• heats space by radiating heat

Fin-Tube Convector (baseboard)

• series of thin vertical tubes spaced closely to max heat transfer to air
• cool air drawn in from below by convection, and heated by contact with fins and discharged out the top

Question 6

List the 6 main Fuel/Power Sources for heating and cooling systems.

Answer 6

1. Natural Gas
   
   • burns clean / no storage rqrd
2. Propane
   
   • burns clean / >$ natural gas
3. Oil
   
   • efficient and rqrs delivery /storage tanks
4. Coal
   
   • rarely used in residential and only sometimes in commercial
5. Electricity
   
   • clean /compact /costly
6. Properly harvested wood
   
   • sustainable energy source
   • causes poor IAQ and air pollution

Question 7

What are the primary and environmental factors of human comfort?

Answer 7

Temperature, humidity, air movement, temperature radiation to and from surrounding services, air quality, sound, vibration, and light.

Question 8

What is the water pressure in City supply systems and how many storeys can be supplied without a pump?

Answer 8

50 PSI - 6 STOREYS

Question 9

How is water supplied above 6 storeys?

Answer 9

The water is pumped up to a rooftop reservoir & gravity downfed.

Question 10

List the sequence from supply main to water fixture

Answer 10

1 - WATER MAIN

2 - CURB BOX

3 - WATER METER

4 - PAST SHUT OFF VALVE

5 - HOT WATER TANK

6 - RISERS

7 - BRANCHES

8 - FIXTURES

Question 11

Minimum slope of a sanitary drain?

Answer 11

1-2%

Question 12

Function of a vent in a sanitary system

Answer 12

• Lead to the outside : roof
• Allows septic gas to escape
• Prevents siphoning of the gases back into the house by creating a seal
• Allow oxygen into the system : breakdown of waste
• Ensures air pressure remains balanced

Question 13

Function of a trap in a sanitary system

Answer 13

• Seals sewer gasses so they cannot escape the fixture

Question 14

Btu

Answer 14

The amount of heat required to raise the temperature of 1 lbm of water 1dF

Question 15

Joule (J)

Answer 15

A measure of energy, one joule is a newton meter, or the force of 1 N acting through a distance of 1 m. One joule is 1/4.184 the amount of heat required to raise one gram of water by 1dC. One Btu equals about 1.055 kJ.

Question 16

Coefficient of heat transmission

Answer 16

The overall rate of eight blow through any combination of materials, including air spaces and air layers on the interior and exterior of a building assembly.

Question 17

Conductance

Answer 17

The number of British thermal units per hour that passes through 1 ft.² of homogeneous material of a given thickness when the temperature differential 1°F.

Question 18

Dew Point

Answer 18

The temperature at which water vapor in the air becomes saturated and begins to condense two drops of water.

Question 19

Dry-bulb temperature

Answer 19

The temperature of the air-water mixture as measured with a standard dry-bulb thermometer.

Question 20

Enthalpy

Answer 20

The total heat in a substance, including latent heat and sensible heat.

Question 21

Latent Heat

Answer 21

Heat that causes a change of state of a substance, such as the heat required to change water into steam. The amount of heat required to change the state of a substance is much greater than the heat required to raise the temperature of the substance (sensible heat).

The average value of latent heat per lb of moisture is 1061 Btu (1120 kJ).

Question 22

Resistance

Answer 22

The number of hours needed for one Btu to pass through one square foot of material or assembly of a given thickness when the temperature differential is 1°F. It is the reciprocal of conductance.

Question 23

Sensible heat

Answer 23

Heat that causes a change in temperature of a substance but not a change of state. For example, the sensible heat required to raise the temperature of 1 lbm of water from 50°F to 100°F is 50 Btu (53 kJ).

Question 24

Specific heat

Answer 24

The number of Btus (joules) required to raise The temperature of a specific material by 1°F. Specific heat is a measure of a material capacity to store heat as compared with the storage capacity of water.

Question 25

Wet-bulb temperature

Answer 25

The temperature of the air as measured with a sling psychrometer. The wetbulb temperature is a more critical measure heat because it is an indicator of stress when the human body is near the upper limit of temperature regulation by perspiration.