Chapter 5 HW Questions - Exam 2

A typical commercial interior space will have an internal heat gain from lights, people, and equipment of about _____ to _____ Btu/hr* ft2.

10; 25

A ton of refrigeration is equal to ___________ Btu's per hour.

12,000

Ballasts introduce about ____% to 30% more heat into the space, so the ballast factor is typically 1.15 to 1.30.

15

1 Watt is equal to _______ Btu/hr.

3.41

In a typical direct expansion cooling system, approximately ____% of the cooling is dedicated to lowering the humidity.

35

CFM per ton

400

The most basic and least accurate of the load calculation methods is to use a rule of thumb method of ________ ft2 to ______ ft2 of floor area per ton of cooling required based upon geographic location.

400; 600

In a typical direct expansion cooling system, approximately ____% of the cooling is dedicated to lowering the temperature.

65

The typical inside design temperature range for cooling in most U.S. homes is usually from ____ F to ____ F.

74; 78

Heat released from an average adult female has been found to be about _____% of an average adult male.

85

Why are should each room be sized separately?

Because each room cooling/heating load will be different depending on what is in the room. By knowing each individual room or zone load, the designer can determine duct or pipe size required to deliver the necessary conditioned air or water to the room or space.

In the case of solar transmission for transparent/translucent elements, the ______ relates to the fraction of radiant energy that is stored in or discharged from the interior thermal mass of the building.

CLF (Cooling Load Factor)

__________ is a time quantity developed by the HVAC industry to specify the number of hours that a cooling system would typically operate at a specific geographical location.

Cooling Load Hours

Adding a safety factor of 50% is acceptable for sizing DX cooling systems.

False

All buildings should have their loads calculated as a total load, not a room by room load calculation.

False

GLF stands for

Glass Load Factor

__________relate to the energy required to cool and dehumidify unconditioned air that has leaked into the building space through the building envelope.

Infiltration Heat Gains

____________ is heat gained through occupants, lights, equipment, computers, and appliances that reject heat into the occupied space.

Internal Heat Gains

_________ is the energy required to change the state of a substance from solid to liquid or a liquid to gas.

Latent Heat Gains

The cooling load is estimated for summer design conditions that typically occur during __________.

Midday

Perimeter or external zones include rooms and spaces with at least _____ exterior wall.

One

The _______________________ is related to the mean temperature swing on the design day—that is, the average difference between the maximum and minimum dry bulb temperatures during the hottest month.

Range of Dry Bulb Temperature

___________ is a value represented by the ratio of solar heat gain through a glazing system under specific conditions to the solar gain through reference glazing (1/8 in clear single glazing) under the same conditions.

SC (Shading Coefficient)

Residential air conditioning systems are rated by the ___________.

SEER OR EER

The ___________ is the fraction of external solar radiation that is admitted through a window or skylight, both directly transmitted, and absorbed and released inward.

SHGC

__________ is the heat that is associated with a change in temperature of a substance.

Sensible Heat Gains

___________ is the energy that a building absorbs from solar energy striking its exterior and conducting to the interior or energy transmitted through windows and being absorbed by materials in the building interior.

Solar Heat Gains

One of the most common problems encountered in HVAC cooling system design is improper sizing of equipment.

True

People actually introduce moisture into a space without having to open windows or introduce infiltration.

True

The use of awnings, roof overhangs, shutters, and solar screens affect the entry of solar radiation.

True

Zoning can be accomplished by having separate equipment or a separate sensor/control arrangement in each space.

True

__________ are tied to the energy required to condition (cool, dehumidify) outside air that is mechanically introduced into the building to maintain occupant comfort and avoid adverse health effects.

Ventilation Heat Gains

Which windows generally have the highest GLF?

West

Commercial cooling systems are rated by the ___________.

kW/ton