Short answer type questions of Principles of Food Engineering
Q 1.
Define specific heat?
Ans. The
specific heat is the amount of heat per unit mass required to raise the
temperature by one degree Celsius without change in surface. It is denoted by
Cp. SI unit of heat capacity is kJ/ (kg K).
Q 2.
Define enthalpy?
Ans. Enthalpy is a thermodynamic quantity
equivalent to the total heat content of a system. It is equal to the internal
energy of the system plus the product of pressure and volume
Q 3.
What are the main functions of baffles in heat exchangers?
Ans. 1. Supports the
tube
2. Maintain
the tube spacing
3. Direct the
flow of fluid in the desired pattern through the shell side.
Q 4.
Define Derived units?
Ans. Derived
units are algebraic combinations of base units expressed by means of multiplication
and division. For simplicity, derived units often carry special names and
symbols that may be used to obtain other derived units. Ex. Joule, Newton,
Volt, Watt etc.
Q 5.
What do you understand by holding tube in pasteurizer?
Ans. The
holding tube is an important component of the pasteurization system. Holding
tubes provide a fixed volume of tubing to "hold" a product for a
set period of time at a given flow rate. This is required for processes,
like pasteurization, sterilization, thermal deactivation, or tempering,
that require a dwell time at a given temperature.
Q 6.
Define thermal conductivity?
Ans. Thermal
conductivity is a measure of the ability of a material to transfer heat. It may
be defined as the thermal conductivity is the heat energy transferred
per unit time and per unit surface area, divided by the temperature difference.
An SI unit for thermal conductivity is watt per meter Kelvin.
Q 7.
Define Manometer?
Ans. Manometer
is an instrument for measuring the pressure of a fluid or gas, consisting of a
tube filled with a liquid. A common simple manometer consists of a U shaped tube of glass filled with some
liquid. Typically the liquid is mercury because of its high density.
Q 8.
What do you understand by scaling/fouling in a heat
exchanger?
Ans. Fouling is
the deposition and accumulation of unwanted materials such as scale, algae,
biofilm, mussels, organic matter and insoluble salts on the internal surfaces
of heat exchangers. Fouling can cause efficiency loss and increased cost of
operation.
Q 9.
Define Boilers?
Ans. Boiler is
a closed vessel in which water or other liquid is heated by using gas,
oil, electricity, or coal to generate hot fluid or steam or vapor.
Q 10.
Enlist any Four SI units?
Q 11.
Define Ideal fluid flow.
Ans. In ideal
flow no friction exists between two fluid layers and the boundary wall. Such a
flow is imaginary but for all theoretical wall fluid may be assume to ideal.
Q 12.
Define Regenerative type of heat exchanger.
Ans. Regenerative
heat exchangers, also referred to as capacitive heat exchangers or
regenerators, alternately allow warmer and cooler fluids to flow through the
same channel. In this type of heat exchanger heat from the hot fluid is
intermittently stored in a thermal storage medium then the fluid is displaced
with the cold fluid, which absorbs the heat.
Q 13.
Enlist
name of four heat exchangers?
Ans Plate type heat exchanger, Shell and tube
type, scraped surface, extended surface or fin type, Spiral type, etc
Q 1.
Define
Viscosity?
Ans Viscosity is
a resistance of a fluid which is being deformed by either shear
stress or tensile stress. Viscosity represented by the
symbol η "eta". The SI unit of viscosity is the pascal
second [Pa s].
Q 2.
Define
autoclave?
Ans An autoclave is a
pressure chamber used to sterilize equipment and supplies by
subjecting them to high pressure saturated steam at 121 °C for around
15–20 minutes depending on the size of the load and the contents.
Q 3.
Define
Convection?
Ans Convection uses the motion of fluids to
transfer heat. When a fluid, such as air or a liquid, is heated and then
travels away from the source, it carries the thermal energy along. This type of heat transfer is called convection.
Q 4.
Define
Base Unit?
Ans A base unit (also referred to as a fundamental unit) is a unit adopted for measurement of a
base quantity. The SI
system is based on a choice of seven well-defined units. The units are Second,
Meter, Kilogram, Ampere, Kelvin, Mole, and Candela.
Q 5.
Define
Porosity?
Ans Porosity is
that portion of the material volume occupied by pore spaces. The void space can
be describing the porosity which is expressed as volume not occupied as good
material. Porosity is the
percentage of air between the particles compared to a unit volume of particles.
Q 6.
Give two
derived units with symbol?
Ans Newton (N), Joule (J), Watt (W), Volt (V),
Ohm ( Ω), Coulomb (C) etc
Q 7.
Define
Latent heat
Ans The quantity of heat absorbed or released by a substance undergoing a
change of state, such as
ice changing to water or water to steam, at
constant temperature and pressure. Two of the more common
forms of latent heat (or enthalpies or energies) encountered are latent
heat of fusion (melting) and latent heat of vaporization (boiling).
Q 8.
Define
wet bulb temperature?
Ans Wet-bulb temperature is determined
when air is circulated past a wetted sensor tip. The moisture evaporates,
lowering the temperature recorded by the thermometer. Less moisture in the air
will result in a faster rate of evaporation and therefore a colder reading.
Q 9.
Define
positive displacement pump?
Ans Positive
displacement pump (PDP) is a type of pump in which a moving fluid
is captured in a cavity and then discharges that fixed amount of fluid. The
displacement of fluid takes place by some parts like plunger, piston, diaphragm
etc. some of these pumps have expanding cavity at the suction side and a
decreasing cavity at the discharge side.
Q 10.
What do
you understand by Flow diversion valve in pasteurizer?
Ans Flow
diversion valve remotely activated valve which is located downstream from the
holding tube. A temperature sensor located at the exit to the holding tube
activates the FDV. FDV maintain direction of flow according to the temperature
of fluid following.
Q 11.
Define
specific gravity?
Ans The specific gravity is the ratio between the density of an object,
and a reference substance. Usually water
is taken as reference substance, has a density of 1 gram per milliliter
or 1 gram per cubic centimeter. The specific gravity can tell us, based on its
value, if the object will sink or float in our reference substance. The
specific gravity has no unit because the units of the
numerator and the denominator are the same,
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