Q1. Which among the following is a type of boiling?

1. Interface evaporation
2. Nucleate boiling
3. Film boiling
4. All of the above

ANSWER – 4. All of the above

• Explanation: Interface evaporation, nucleate boiling, and film boiling are the three types of boiling. In the first phase of interface evaporation, a liquid comes into contact with a heated surface to produce vapour, which rises due to convection, generating convection currents that circulate the liquid; this is known as free or natural convection. As the temperature rises, the liquid heats up, the bubbles do not condense and aid in evaporation, and this phase is known as nucleate boiling. During the next regime, the bubble film is unstable, reforming and collapsing.

READ MORE – FOOD TECHNOLOGY (24/08/2021)

Q2. _______ is defined as the stress causing the free surface of the fluid to contact is tangential to the surface.

1. Surface tension
2. Pressure
3. Heat transfer
4. Equilibrium

ANSWER: 1. Surface tension

• Explanation: The stress that causes the free surface of the fluid to contact is known as surface tension; this stress is tangential to the surface. Due to surface tension, the pressure inside a bubble, p1, is greater than the surrounding liquid pressure, p. The difference between the two pressures for a bubble in equilibrium is derived by the equation p = p1-p = 2s/r, where s = surface tension kg/m and r = curvature radius of bubble, m, according to the Laplace equation.

READ MORE – FOOD TECHNOLOGY (04/09/2021)

Q3. ________  is defined as the effort required detaching the liquid from the unit area of the hard surface.

1. Cohesion
2. Adhesion
3. Surface tension
4. All of the above

ANSWER: 2. Adhesion

• Explanation – Visual observation has shown that vapour bubbles form only on the heated surface, where liquid superheat is greatest, and only at specific spots on that surface known as commencing boiling. Evaporation beginning points may be found on surfaces with the least amount of adhesion. The effort required to separate a liquid from a unit area of a hard surface is known as adhesion.

READ MORE – FOOD TECHNOLOGY (14-09-2021)

Q4. The peaking point is a critical point and heat flux at this critical state is called _____.

1. Nucleate boiling
2. Film condensation
3. Critical flux
4. Critical heat transfer

ANSWER: 3. Critical flux

• Explanation: In the next regime, after interface evaporation, the phenomenon of nucleate boiling begins. As the temperature rises, the liquid heats up, the bubbles do not condense and aid in evaporation, and this phase is known as nucleate boiling. As seen by the crest of the curve, this phenomenon has a limit. The critical point is the peaking point, and critical heat flux is the heat flow at this critical state.

READ MORE – FOOD TECHNOLOGY (24/07/2021)

Q5. The direct type condenser includes which among the following types

1. Jet condenser
2. Parallel type condenser
3. Counter type condenser
4. All of the above

ANSWER – 4. All of the above

• Explanation – A heat exchanger in which cooled water is sprayed into the unit where vapour is to be condensed is known as a jet condenser. A parallel flow or counter flow condenser is a sort of jet-type condenser. In most cases, the parallel flow condenser is used as a wet condenser, whereas the counter-current flow condenser is used as a dry condenser. Air and water are evacuated at the same temperature in a parallel flow condenser, whereas non-condensables are removed at the temperature of the entering water in a counter-current condenser.

READ MORE – FOOD TECHNOLOGY (23/06/2021)