PIPE Elements 5

A rule of thumb is that the COP improves by_______for each ⁰C the evaporating temperature is raised or the condensing temperature is lowered.
a. 2 to 4%
b. 6 to 7%
c. 1 to 5%
d. 6 to 10%

Diagram frequently used in the analysis of vapor comprrssion cycle is the
a. T-s diagram
b. P-h diagram
c. P-V diagram
d. h-s diagram

Two common sources of irreversibilities are
a. pressure and temperature
b. specific volume and fuel
c. volume and temperature
d. fluid frictions and heat transfer

Was the first commercially used refrigerant in vapor compression system.
a. Ammonia
b. R-11
c. Ethyl alcohol
d. Ethyl ether

the advantages of ammonia over other refrigerants are its
a. high power
b. high refrigerating effect
c. none flammable
d. low cost and higher COP

Is predominantly used in food refrigeration facilities
a. Ammonia
b. R-12
c. R-12
d. water

Is used primarily in large-capacity water chillers serving air conditioning systems in buildings
a. R-11
b. R-12
c. ethyl chloride
d. Ammonia

Is used in domestic refrigerators and freezers

is used in window air-conditioners

Two important factors which need to be considered in the selection of a refrigerant are the temperatures of the two media are the
a. surroundings and type of refrigerant
b. combustible and rating
c. refrigerated space and the environment
d. none of these

To have heat transfer at a reasonable rate

The temperature of the refrigerant on the condenser side depends on the medium to which heat is
a. added
b. rejected
c. constant
d. none of these

lower temperatures in the condenser can be maintained if the refrigerant is cooled by water instead of
a. brine
b. water
c. air
d. gas

In the case of heat pumps

Are generally more expensive to purchase and install than other heating systems

The most common energy source for heat pump is
a. compressed air
b. atmospheric air
c. vacuum air
d. re-circulated air

The major problem with air-source system is frosting

Both the capacity and the efficiency of a heat pump fall significantly at
a. medium temperature
b. maximum temperature
c. allowable temperature
d. low temperature

Heat pumps and air conditioners have the same
a. suction
b. evaporator
c. refrigerants
d. mechanical components

For large industrial applications

At temperatures above the critical-point value

__________cycle is also known as gas refrigeration cycle
a. Reversed Brayton
b. Reversed Rankine cycle
c. Reversed adiabatic cycle
d. none of these

Another form of refrigeration which becomes economically attractive when there is a source of inexpensive heat energy at a temperature of 100 to 200⁰C is
a. Steam-jet refrigeration
b. Ammonia refregeration
c. Absorption refrigeration
d. Vapor compression cycle

The most widely used absorption is the ammonia-water system

The circuit which incorporates both thermal and electrical effects is called
a. thermoelectric circuit
b. thermocouple device
c. battery
d. none of these

The difference between Cp and Cv________ as the absolute temperature approaches zero.
a. approaches infinity
b. 100
c. approaches zero
d. approaches finit value

If Joule Thomson coefficient is less than 0

Composition of mixture that specifying the number of mole of each component is called
a. gravimetric analysis
b. ultimate analysis
c. proximate analysis
d. molal analysis

Composition of mixture that specifying the number of mass of each component is called
a. Orsat analysis
b. gravimetric analysis
c. heat analysis
d. proximate analysis

Is the ratio of mass of component to the mass of the mixture.
a. mass mole
b. mass fraction
c. mass disintegration
d. mass long

The pressure of a gas mixture is equal to the sum of the pressure each gas would exert if it existed alone at the mixture
a. pressure and temperature
b. volume
c. density
d. temperature and volume

The volume of a gas mixture is equal to the sum of the volumes each gas occupy if it existed alone at the mixture
a. pressure and volume
b. temperatire and density
c. temperature and pressure
d. humidity

At temperatures below the critical temperature

Is a mixture of nitrogen

The air in the atmosphere normally contains some water vapor and is referred to as
a. zero pressure
b. gage pressure
c. atmosphere
d. none of these

The air that contains no water vapor is called
a. zero air
b. saturated air
c. dry air
d. humid air

The composition of dry air remains relatively constant but the amount of water vapor
a. is fixed
b. changes
c. is constant
d. none of these

The temperature of air in an air-conditioning applications ranges from about
a. -10 to 50⁰C
b. -10 to 40⁰C
c. -12 to 10⁰C
d. none of these

The partial pressure of water vapor is usually referred to as the
a. gas
b. vapor
c. steam
d. mixture

Is the pressure the water would exert if it existed alone at the temperature and volume of the mixture
a. vapor pressure
b. saturated pressure
c. vapor temperature
d. none of these

Water vapor is an ideal gas

In psychrometric chart

The enthalpy of water vapor in air can be taken to be equal to the enthalpy of the saturated vapor at
a. the same specific volume
b. the same entropy
c. the same internal energy
d. the same temperature

The mass of water vapor present in a unit mass of dry air is called
a. specific humidity
b. specific volume
c. percent humidity
d. none of these

The specific humidity of dry air is
a. one
b. 100%
c. zero
d. 90%

By adding humidity ratio to dry air

Air is said to be saturated with moisture is known as
a. saturated vapor
b. saturated liquid
c. saturated air
d. none of these

Any moisture introduced into saturated air will
a. vaporized
b. condense
c. solidify
d. moisturized

The amount of moisture in the air has a ________ on how comfortable we feel in an environment
a. definite forms
b. definite moisture
c. definite characteristics
d. definite effect

is the ratio of water-vapor mixture and saturation pressure at given temperature.
a. percent saturation
b. relative humidity
c. humidifier
d. none of these

The relative humidity ranges from 0 for dry air to 1 for
a. superheated air
b. dry air
c. stratified air
d. saturated air

The amount of moisture in air depends on its
a. pressure
b. volume
c. temperature
d. humidity

The relative humidity of air changes with temperature even when its specific humidity
a. increase
b. decrease
c. remains constant
d. none of these

The enthalpy of atmospheric air is expressed per unit mass of
a. water
b. cold air
c. dry air
d. none of these

The ordinary temperature of atmospheric air is frequentlybrefered to as the
a. wet bulb temperature
b. dry bulb temperature
c. allowable temperature
d. none of these

Is defined as the temperature at which condensation begins if the air is cooled at constant temperature
a. allowable maximum temperature
b. dew point temperature
c. co-valent temperature
d. equilibrium temperature

The dew point temperature is the saturation temperature of water corresponding to the
a. vapor temperature
b. vapor mixture
c. vapor pressure
d. none of these

As the air cools at constant pressure the vapor pressure
a. increase
b. decrease
c. remains constant
d. none of these

The ordinary temperature and the dew-point temperature of saturated air are
a. different
b. slight difference
c. unique
d. identical

The adiabatic saturation process involves no interaction

In general

For saturated air

The rate of heat generated by body:Adult male-87 watts when sleeping

The deep body temperature of healthy person is maintained constant at
a. 27⁰C
b. 37⁰C
c. 47⁰C
d. 48⁰C

Heat transfer is proportional to
a. pressure difference
b. temperature difference
c. density
d. penetration

The hands feel painfully cold when the skin temperature reaches
a. 0⁰C
b. 5⁰C
c. 10⁰C
d. 15⁰C

Factor that affects human comfort is heat transfer by ________between the body and surrounding surfaces
a. convection
b. radiation
c. conduction
d. none of these

The comfort of the human body depends primarily on
a. dry bulb
b. relative humidity
c. air motion
d. all of these

Most people feel comfortable when the environment temperature is between
a. 22⁰C and 27⁰C
b. 20⁰C and 40⁰C
c. 34⁰C and 40⁰C
d. none of these

Is a measure of air's ability to absorbore moisture
a. percent saturation
b. relative humidity
c. specific volume
d. none of these

Most people prefer a relative humidity of
a. 20 to 30%
b. 30 to 40%
c. 40 to 60%
d. none of these

Air motion also plays important role in
a. surroundings
b. cooling
c. human comfort
d. none of these

Removes the warm

Most peiple feel comfortable at an airspeed of about
a. 12m/min
b. 13m/min
c. 15m/min
d. none of these

Other factors thar affect comfort are
a. cleanliness
b. odor
c. noise and radiation effect
d. all of these

Maintaining a living space or an industrial facility at the desired temperature and humidity requires some process called
a. refrigeration process
b. air-conditioning process
c. cooling process
d. none of these

Simple heating process of air-conditioning
a. minimizing the temperature
b. limiting the temperature
c. raising the temperature
d. none of these

Simple cooling process of air-conditioning
a. maximizing the temperature
b. hinder the temperature
c. lowering the temperature
d. none of these

___________of air-conditioning is adding moisture to air
a. humidifying process
b. dehumidifying process
c. heating process
d. none of these

_______of air-conditioning is removing moisture.
a. dehumidifying process
b. humidifying process
c. cooling process
d. none of these

During simple heating and cooling process has a ______humidity ratio
a. increasing
b. decreasing
c. constant
d. none of these

Air is commonly __________in winter and cooled and dehumidified during summer.
a. heated and humidified
b. cooling and dehumidified
c. adiabatic saturation
d. none of these

Dry bulb temperature is increasing during
a. cooling process
b. heating process
c. cooling and heating process
d. none of these

Relative humidity decreases during
a. heating process
b. cooling process
c. isothermal process
d. none of these

Dry bulb temperature_______during cooling process.
a. increases
b. decreases
c. remains constant
d. none of these

Problems associated with the low relative humidity resulting from simple heating can be eliminated by
a. cooling
b. dehumidifying
c. humidifying the heated air
d. none of these

The specific humidity of air remains constant during a simple cooling process

Evaporative coolers is also known as
a. heat exchanger
b. swamp controllers
c. swamp coolers
d. none of these

The evaporative cooling process is essentially identical to the adiabatic saturation process since the heat transfer between the air stream and the surroundings is usually
a. positive
b. negative
c. negligible
d. none of these

The______folows a line of constant wet-bulb temperature on the psychrometric chart
a. evaporative cooling process
b. condensive cooling process
c. direct cooling process
d. none of these

The heat transfer with the surroundings is usually small

Mixing process normally involve no work interactions

A_______is essentially a semi-enclosed evaporative cooler
a. dry cooling tower
b. wet cooling tower
c. forced draft cooling tower
d. none of these

________looks like an ordinary chimney.
a. Natural draft cooling tower
b. Forced draft cooling tower
c. natural cooling tower
d. none of these

_______ do not require any external power.
a. Natural draft cooling tower
b. Forced draft cooling tower
c. Natural cooling tower
d. none of these

The natural draft cooling towers are_________in profile
a. parabolic
b. hyperbolic
c. circular
d. none of these

The ideaofbcooling tower started with the
a. cooling pond
b. ejector pind
c. spray pond
d. none of these

Is basically a large lake open to the atmosphere
a. forced pond
b. natural pond
c. cooling pond
d none of these