Short answer type questions of Principles of Food Engineering

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?

Ans.     Meter (m), Second (s), Kelvin (K), Kilogram (kg), Mole (mole), Ampere (A), Candela (cd)

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,