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ABE 2 Second Exam > Module 4: Psychrometry > Flashcards

Module 4: Psychrometry Flashcards

1
Q

the study of the properties of mixtures of air and water vapor

A

psychrometry

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2
Q

air and water vapor at diff conditions affects the product during drying and storage operations

true or false

A

true

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3
Q

it is a binary mixture of dry-air and low-pressure water vapor

A

moist air

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4
Q

components of dry-air

A
  • nitrogen
  • oxygen
  • argon
  • carbon dioxide
  • rare gases
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5
Q

for pure substances, two properties are sufficient, while for binary mixtures, three properties are needed to completely define their state

true or false

A

true

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6
Q

the major physical properties of air that affect the drying rate of grains are

A
  • RH or humidity ratio
  • dry-bulb & wet-bulb temperature
  • specific volume
  • enthalpy
  • dew point temp
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7
Q

physical properties of air that affect the drying rate of grains

measured by the ordinary thermometer

A

dry bulb temp

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8
Q

physical properties of air that affect the drying rate of grains

dry bulb temp is the horizontal lines in the chart

true or false

A

false; it’s the vertical lines

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9
Q

physical properties of air that affect the drying rate of grains

air temp measured by an ordinary thermometer whose glass bulb is covered by a wet cloth or gauze

A

wet bulb temp

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10
Q

physical properties of air that affect the drying rate of grains

air temp at which moisture condenses at the surface

A

dewpoint temp

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11
Q

physical properties of air that affect the drying rate of grains

scale is the same as the wet bulb scale which is on the face of the shoe

A

dewpoint temp

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12
Q

physical properties of air that affect the drying rate of grains

dewpoint temp are lines parallel to the x axis

true or false

A

true

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13
Q

physical properties of air that affect the drying rate of grains

amount of water vapor per unit dry air

A

absolute humidity

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14
Q

physical properties of air that affect the drying rate of grains

y-axis or the ordinate (the back of the shoe)

A

absolute humidity (or HR)

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15
Q

physical properties of air that affect the drying rate of grains

relative humidity and dew points are at the same lines

true or false

A

false; dew point temp are the horizontal lines while RH are the lines sloping upwards

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16
Q

physical properties of air that affect the drying rate of grains

lines are the same as the dew point temp lines

A

absolute humidity

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17
Q

physical properties of air that affect the drying rate of grains

ratio of partial pressure of water vapor to the saturation pressure of pure water at the same temperature

A

relative humidity

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18
Q

physical properties of air that affect the drying rate of grains

face of the shoe

A

relative humidity

19
Q

physical properties of air that affect the drying rate of grains

defined as the volume occupied by a kilogram of dry air

A

specific volume

20
Q

physical properties of air that affect the drying rate of grains

these are the diagonal lines having a higher slope compared to wet bulb lines

A

specific volume

21
Q

physical properties of air that affect the drying rate of grains

heat content of the air (denoted by h)

A

enthalpy

22
Q

physical properties of air that affect the drying rate of grains

it is essential in the calculation of the energy requirement of any process involving air a the medium

A

enthalpy

23
Q

_______ ______: cubic meter/kg dry air
enthalpy : ___________

A

specific volume: cubic meter/kg dry air
enthalpy : kilo Joules/kg

24
Q

psychrometric processes

A
  1. sensible heating or cooling
  2. humidification
    a. adiabatic humidification
    b. non adiabatic humidification
  3. cooling and dehumidification
    a. moisture condensation
25
Q

psychrometric processes

involves the increase or decrease in the air temp without changing its humidity ratio

A

sensible heating or cooling

26
Q

psychrometric processes

sensible heating or cooling is a process that’s depicted as a horizontal line in the chart extended to the _______ for sensible heating and to the _______ for cooling

A

right; left

27
Q

psychrometric processes

process of adding water to the air

A

humidification

28
Q

psychrometric processes

on heat exchange with surroundings, constant wet bulb temperature, dry bulb temperature decreases

A

adiabatic humidification

29
Q

psychrometric processes

heat is added, net heat added is positive, dry bulb temperature can increase along with moisture content

A

non adiabatic humidification

30
Q

psychrometric processes

decrease in dry bulb temp and HR

A

cooling and dehumidification

31
Q

psychrometric processes

cooling and dehumidification, the total heat removed is equal to the total heat removed in the ________ ____

A

cooling coil

this principles is referred as the refrigeration capacity

32
Q

psychrometric processes

occurs when moist air is cooled to a temperature below its initial dew point

A

moisture condensation

33
Q

is the process where ambient air is heated to a desired drying temperature at a constant humidity and vapor pressure

A

heating

34
Q

process where the temperature of the heated air decreases during drying, approaching 100% RH and constant wet bulb temp

A

cooling

35
Q

where are psychrometric principles applied?

A
  • load calculations
  • air-conditioning systems
  • cooling and dehumidifying coils
  • cooking towers
  • evaporative condensers
36
Q

component of moisture air consisting of composition of gases

A

dry-air

37
Q

component of moisture air which is a very low-pressure steam, the amount of which could vary from zero to a mac value for a given pressure and temp

A

water-vapor

38
Q

major physical properties of air that affect the drying rate of grains

A
  • RH
  • dry-bulb temp
  • specific volume
  • enthalpy
39
Q

refers to the mole fraction of water vapor in moist air to the mole fraction of water vapor in saturated air at the same temperature and pressure

A

relative humidity

40
Q

process by which the wet-bulb thermometer cools due to water evaporation

A

evaporative cooling

41
Q

knowing both the dry-bulb and wet-bulb temperatures allows you to determine the ______ _______ of the air using a psychrometric chart

A

relative humidity

42
Q

________ ______ of the drying air affect the power required by the fan

A

specific volume

43
Q

enthalpy of the mixture of dry air and water vapour is the sum of the enthalpy of the dry air and the enthalpy of the water vapour

true or false

A

true

44
Q

the zero value of the water vapour is saturated liquid water at __ degree Celsius, this is the same reference point used for steam

A

0

ABE 2 Second Exam (6 decks)

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