CEM 350 - Exam 2 Study

Diffusers

Generally in a general duct work system, the duct work is constructed from galvanized steel. However, flexible duct in short segments is preferred for ease of construction to connect...

30%

Ductwork construction is approximately _____ of the cost of an HVAC air-based system

Duct mastic

For sealing ducts at connection points to air handling units, the recommended material is _______

2

The problem with utilizing flexible duct for an entire ductwork system is that flex duct has ____ times the friction or resistance to air flow compared to galvanized steel ductwork

1:1

Concerning ductwork fabrication and construction , the preferred aspect ratio would be ______

Centrifugal ; axial

Concerning air-handling fans, the two most common fan designs are _____ and ____________

Higher cost

In a filter for an HVAC system, the key problem with a pleated-type filter compared to a flat filter is _____.

Ceiling height

Comparing the selection of galvanized steel ductwork, round duct is use less than rectangular because of ________ issues

Damper Control

A feature in an HVAC system for a relief air scheme can be accomplished at the lowest cost by ________.

Natural gas: 5x10^-6 $/BTU, No. 2: 7.14x10^-6 $/Btu cost per Btu is less for natural gas

If gas is available at $0.50 therm and No. 2 oil is available at $1 per gallon, which will be the more economical fuel source based on the cost per Btu?

$6.25

If the gas is available at $0.50 per therm and the efficiency of the utilization is 80 perfect, what is the net cost of heating energy in dollars per million Btu?

1. Where it will minimize the amount of piping required

2. Where noise is generated from the machine wont be heard and disturb occupants

3. Where it has good access to combustible air and a fuel supply

Select all that apply. Which factors should be considered in deciding where to put a central boiler plant for a large building.

Annual Fuel Utilization Efficiency

AFUE

92-95%

What is the nominal AFUE of impulse-type furnaces

blow-down

Boiler _____is a process of removing impurities

5.86

A vapor compression refrigeration machine uses 30kW of electrical power to produce 50 tons of cooling. What is its COP?

Either helical or centrifugal compressors

Chilled water systems use water cooled condensers with what types of compressors installed?

R-410A

What has the refrigerant R-22 been replaced with?

1. Because it is extremely toxic

2. Because it is flammable

Ammonia is an environmentally friendly refrigerant with high performance that is cheap compared to other refrigerants. if it is so great, why is it not used in most applications?

1,500,000 gal

Approximately how much chilled water storage would be required to reduce chiller load by 250 tons for a period of 6 hours

3,000 gal

(1,500,000/10)

Approximately 1,500,00 gal of chilled water storage would be required to reduce chiller load by 250 tons for a period of 6 hours. How much ice storage is required?