Food Engineering Operations - I — Winter 2018

Differentiate between shallow and deep bins used for grain storage.

Calculate the appropriate Grashof Number when the external surface of a heating coil 30 mm diameter having surface temperature 800C in water at 200C (ρ = 1000kg/m3, Pr = 6.95, β = 0.227x10-3 K-1, µ = 1x10-3kg/ms.

What is Fourier’s law? Derive an expression for heat conductance for composite wall.

Define the process of diffusion and state the application of Diffusion in food industry.

Discuss the machine and operational factors for the design of air screen cleaners.

(i) Define fineness modulus? What does it indicates? (ii)The sieve opening and the mass retained on the sieves during sieve analysis is given below in the table. Calculate mass mean diameter and volume surface mean diameter and volume mean diameter. Sieve opening (mm) 2.032 1.405 1.000 0.500 0.211 Pan Mass fraction retained --- 0.077 0.424 0.304 0.155 0.040

(i) What are laws for the energy calculation for size reduction? (ii) How much power is required to crush 2.5 tonne/hour of a material if 80% of feed passes through IS sieve No. 480 (4.75 mm opening) and 80% of the product passes through IS sieve No. 50 (0.5 mm opening)? Given the work index of the material as 6.5.

Define the followings : 1. Particle and Material density 2. Adhesiveness and Cohesiveness 3. Sphericity and Roundness

Discuss the convective mass transfer. List out the parameters on which convective mass transfer depends upon.

Afruit juice is passing through a hot pipe of 7.5cm diameter and 3.3m long @60 lpm and the wall temperature is 1200C. The juice is entering at 250C and is leaving at 750C. Find the heat transfer coefficient and Nusselt number if the fluid properties are assumed to be those of water. Fluid properties are ρ = 1000 kg/m3, k = 0.6 W/m0C, Cp = 4.2 kJ/kg0C and µ = 1x10-3 Pas

Calculate Prandtl Number when air at 1000C   1 . 4 61 x1 0 -6  .T T 3 / Kg / m s C p  0 . 9 1 7  2 . 5 8 x 1 0  4 T  3 .9 8 x 1 0  8 T 203 kJ/kg K (where Tis the absolute temperature in Kelvin), k = 0.03186 w/mK

Discuss with diagram the moisture and temperature changes in stored grain during summer and winter season.

What do you understand by Texture Profile Analysis (TPA). Draw the diagram of TPA in detail. Define Farcturability, Springiness, Gumminess and Hardness of food products.

Apiece of meat carcase is kept in a deep freezer maintained at -210C. Calculate the radiative heat transfer if the meat carcase is at 280C and has an average area of 0.045m2. The emissivity of carcase is 0.82.

Define the followings and represents with graph 1. Shear thinning 2. Shear thickening 3. Newtonian fluid 4. Non-Newtonian fluid

Astorage structure having smooth wall used for storing rice has diameter of 2.5 m and height 25 m. The characteristics of stored rice are as follows: Minimum bulk density : 720 kg/m3 Maximum bulk density: 830 kg/m3 Minimum angle of internal friction: 25º Maximum angle of internal friction: 30º Minimum angle of friction on smooth wall: 180 Angle of repose: 250 Calculate the load on the bottom, and the lateral pressure thrust at 12 m depth on walls.

Describe the process of mass transfer in gas-liquid system.

Write the followings; 1. Equation of Nusselt Number when flow is laminar 2. Equation of Pecklet, Stamton, Rayleigh and Grashof Number Acomposite wall of a furnace has 2 layers of equal thickness having thermal conductivities in the ratio of 3:2. What is the ratio of the temperature drop across the two layers?

What are the features of transition and control zone when grains flow through circular orifice?

Awall as shown below is made up of two layers (A) and (B). The temperatures are also shown in the sketch. The ratio of thermal conductivity of two layers is k /k = 2. What is the ratio of thickness of two layers? A B

Derive an expression for conduction heat transfer when the pipes are in series.

Mention the types of belt conveyor idlers used in food industry.

Write the principles for the selection of conveying system. Discuss in brief the construction and working of screw conveyor.

Write short notes on (i) Modified atmosphere storage (ii) Pusa Bin