heat transfer & post harvest

forced covection over plate

highest convection heat transfer coefficient

reflectivity

in radiative heat transfer, which of the following perfect reflector properties is equal to unity?

infiltration load

the load added to the cooling equipment when cooled air is displaced by outdoor air entering through cracks around doors and windows when doors are open

tempering

the equalization of moisture or temperature throughout the prduct, bringing a product to a desired moisture content or temperature for processing is called

transient heat transfer

other term for unsteady heat transfer

solids

heat transfer by conduction occurs primarily in

copper

a material that is best thermal conductor

thermal conductivity

a property that measures a materials ability to conduct heat

temprerature-induced density difference

in natural convection, fluid motion is caused by

radiation from a blackbody

the stefan-boltzman law is associated with

q=-kAdxdT

an equation correctly defines heat conduction (fourier’s law)

W/m.K

the unit of thermal conductivity in SI unit is

black body

a surface that absorbs all incident radiation is called

a medium

heat transfer by radiation does not require

conduction

when boiling in a pot, the heat transfer from the stove to the pot is mostly

conservation of energy

the first law of thermodynamics is based on the principle of

internal function

which of the following is a state function

adiabatic

a process in which there is mo heat exchange with sorrounding is called

J/K (Joules/Kelvin)

the unit of entropy in SI unit is

entropy of an isolated system never decrases

the second law of thermodynamics states that

isochoric

which thermodynamic process occurs at constant volume

Boyle’s law

which gas law is used in isothermal processes

temperature only

the internal energy of an ideal gas depends on

H = U + PV

what is the thermodynamic definition of enthalpy (H)?

pressure

which of the following is an intensive property

third law of thermodynamics

a law defines absolute zero

zero

in cyclic process, the change in internal energy is

turbine

a device that converts thermal energy directly into mechanical work

temperature

the zeroth law of thermodynamics helps define

zero

in an isothermal process, the change in internal energy is

two adiabatic and two isothermal process

the carnot cycle is composed of

temperature and heat reservoir

the efficiency of a recersible carnot engine depends on

heat required to raise temperature by 1 kg to 1 K

specific heat is defined as

Joule

SI unit for heat energy

heat into work

a heat engine converts

heat added or removed without changing its temperature

the term “latent heat“ refers to

nRT

for an ideal gas, PV =

pressure

an isobaric process occurs at constant

disorder or randomness

entropy is a measure of

n=1-THTL

the maximum efficiency of a heat engine is given by

1366 W/m²

1.366 kJ/m² = 1.366kW/m²

the solar constant value is ____ W/m²

control surface

characterized as both mass and energy can cross the boundary of a control volume

enthalpy of condesation

the amount of energy required to convert one mole of gas into liquid

extensive

the amount of water flowing in a pressurized drip irrigation pipe os considered as what property

phase equilibrium

a system consisting of a mixture phases, such as liquid water and water vapor, if the composition of the mixture remains constant over time

ICE

which of the following is an adiabatic

otto

which cycle inspired the first patented 4-stroke ICE, also known as the gasoline cycle

convection

three modes of mass transfer are diffucion, migration/advection, and ___

metal with higher sensible heat has a minimal effect in melting

which is true about sensible heat of metal

sensible heat (change in form with change in temperature)

latent heat (changes substance form)

which is true about the difference of latent heat and sensible heat

power covert to heat

other term for the power dissipated

refrigeration cycle

also called the reversed carnot cycle

specific volume

the property of a substance that describes the volume occupied by a unit of mass

BTU

amount of heat needed to raise the temperature of 1 pound to 1 degree farenheit

system

the mass as well as the energy may take place between system and its surrounding

phase equilibrium

a system consisting of a mixture of multiple phases, such as liquid, water and water vapor, if the composition of the mixture remains constant over time.

29% saturated vapor

a quality (x) value of 0.29 indicates

electromagnetic waves

the sun emits energy via radiation and this travels via ____

convection

what heat transfer happend inside dryer’s plenum

decreased heat transfer

what will happen to the rate of heat transfer if the outside radius of a pipe doubled

2nd law

other term for law of entropy in thermodynamics

triple point

the specific temperature and pressure at which its solid, liquid, and gaseous phase can coexist in thermodynamic equilibrium

temperature of heat reservoir only

the efficiency of a carnot cycle depends on

ZERO

in an isothermal process, the change in internal energy is

gases

convection involves heat transfer due to movement of

joule

not a unit of power

adiabatic cycle

characterized by no heat exchange

safe moisture content

a term refers to the moisture content at which hrain is considered safe for storage

cleaning

the removal of foreign materials such as stones and chaffs from hrains is known as

cooling

in paes, it is defined as the process of reducing the temperature of produce to slow down deterioration

drying

term for process of removing excess moisture to prolong storage life is

milling

not typically used to describe mechanical damage in postharvest

grading

practice of grouping produce according to quality parameters is known as

equilibrium moisture content

the moisture content of a product when it is in equilibrium with the surrounding air is called

bulk density

according to paes, the measure of mass per unit volume including air spaces is

aeration

a system or method that allows airflow through stored grains is called

fermentation

in paes it is defined as the transformation of sugar into alcohol or acid by microorganism

maintains its freshnes

the term “shelf life“ refers to the period a product

preservation

the process of maintaining postharvest conditions to minimize quality deterioration

curing

the process of allowing root crops to heal shrface injuries before storage is called

shrinkage

according to paes, the term for the decrease in weight due to water loss is

percentage of impurities removed

what does “cleaning efficiency“ measure

has short shelf life

in postharvest terms, a “perishable“ commodity refers to one that

drying efficiency

this refers to the ratio of actual drying time to the theoretical drying time

cooling

a process that reduces respiration rate of produce

product color

in paes, this does not influence drying rate

storability

the ability of a commodity to resist deterioration over time

bruise

mechanical injury caused by impact or drop is called

moisture weight / total weight

in paes, the product’s “moisture content (wet base)” is calculated as

classify quality

the purpose of grading in postharvest handling

molds

main cause of spoilage in improperly dried grains

moisture loss

the shrinkage of fruits and vegetables is primrily due to

10-12%

the acceptable range of grain moisture content for safe storage in the Philippines

air drying

the process of reducing moisture using heated air is known as

efficiency

the ratio of useful work to total energy input in postharvest machinery

mass of product retained after processing

“product recovery“ in postharvest processing refer to