List of top Agricultural Process Engineering Questions on Thermal Process asked in GATE AG

In an inoculated pack study, 0.5 kg peas per can are thermally processed at 121 °C. One group of cans contains Clostridium spp. spores with an initial spore level of \( 5 \times 10^{10} \) per can. Another group of cans contains Bacillus spp. spores. It is desired to have spoilage probability of 5 in 100 cans after thermal processing. The decimal reduction time of Clostridium spp. and Bacillus spp. at 121 °C are 2.5 minutes and 6.0 minutes, respectively. If all the cans receive the same lethality, the initial number of spores of Bacillus spp. per g of peas is __________ (Answer in integer)
Milk enters at 25°C through the inner pipe of a concentric double pipe heat exchanger. Hot water enters at 82.5°C and flows countercurrently (flow rate = 1.2 kg/s) through the annular region. The diameter of the inner pipe, length of the pipe, and average overall heat transfer coefficient are 60 mm, 6 m, and 2100 W.m\(^{-2}\).K\(^{-1}\), respectively. The average values of specific heat capacity of water and milk are 4.18 kJ.kg\(^{-1}\).K\(^{-1}\) and 3.95 kJ.kg\(^{-1}\).K\(^{-1}\), respectively. The effectiveness of the heat exchanger is 0.572 and the NTU is 1.01. Assuming the steady-state condition and considering \( \pi \) as 3.14, the temperature of hot water at the exit of the pipe is _________ °C. (Rounded off to 1 decimal place)
Three straight metal wires, AC, BC, and CD, having the same length, diameter, and thermal conductivity, are connected as shown in the figure. Heat flows from points ‘A’ and ‘B’ to point ‘C’ and from point ‘C’ to point ‘D’. Temperatures at points A, B, and D are 100 °C, 100 °C, and 40 °C, respectively. Assuming steady-state condition and no heat loss from the wires, the temperature at point ‘C’ is _________°C. (Answer in integer)
The quantity of water needed to increase the moisture content of 50 kg paddy grains from 13% (dry basis) to 35% (dry basis) in the hydrothermal treatment process is _________ kg. (Rounded off to 2 decimal places)
In an inoculated pack study, 0.5 kg peas per can are thermally processed at 121 °C. One group of cans contains Clostridium spp. spores with an initial spore level of \( 5 \times 10^{10} \) per can. Another group of cans contains Bacillus spp. spores. It is desired to have spoilage probability of 5 in 100 cans after thermal processing. The decimal reduction time of Clostridium spp. and Bacillus spp. at 121 °C are 2.5 minutes and 6.0 minutes, respectively. If all the cans receive the same lethality, the initial number of spores of Bacillus spp. per g of peas is __________ (Answer in integer)
The assumption(s) which is/are not correct for deriving the Plank’s equation for estimation of food freezing time:
Three straight metal wires, AC, BC, and CD, having the same length, diameter, and thermal conductivity, are connected as shown in the figure. Heat flows from points ‘A’ and ‘B’ to point ‘C’ and from point ‘C’ to point ‘D’. Temperatures at points A, B, and D are 100 °C, 100 °C, and 40 °C, respectively. Assuming steady-state condition and no heat loss from the wires, the temperature at point ‘C’ is _________°C. (Answer in integer)
The quantity of water needed to increase the moisture content of 50 kg paddy grains from 13% (dry basis) to 35% (dry basis) in the hydrothermal treatment process is _________ kg. (Rounded off to 2 decimal places)
In general, result(s) of blanching fresh fruits and vegetables is/are:
Milk enters at 25°C through the inner pipe of a concentric double pipe heat exchanger. Hot water enters at 82.5°C and flows countercurrently (flow rate = 1.2 kg/s) through the annular region. The diameter of the inner pipe, length of the pipe, and average overall heat transfer coefficient are 60 mm, 6 m, and 2100 W.m\(^{-2}\).K\(^{-1}\), respectively. The average values of specific heat capacity of water and milk are 4.18 kJ.kg\(^{-1}\).K\(^{-1}\) and 3.95 kJ.kg\(^{-1}\).K\(^{-1}\), respectively. The effectiveness of the heat exchanger is 0.572 and the NTU is 1.01. Assuming the steady-state condition and considering \( \pi \) as 3.14, the temperature of hot water at the exit of the pipe is _________ °C. (Rounded off to 1 decimal place)
A copper ball and a steel ball having diameters \(d_1\) and \(d_2\), respectively, are initially at 200°C. Both are cooled to ambient 30°C. If both reach 120°C in equal duration, find ratio \(d_1/d_2\). Assume Biot < 0.1.
The carrot slices (water activity = 0.89) are to be preserved using osmo-dehydration. Addition of salt (NaCl) to 20% sucrose solution (water activity = 0.987) reduces the water activity to 0.85. Find the percentage of NaCl added to the solution. (Molecular mass of sucrose = 342, molecular mass of NaCl = 58.44).
Cheese is packed in a bilayer plastic package made of low density polyethylene (LDPE) and polyethylene terephthalate (PET). Thickness of LDPE and PET in the package are 1.5 mm and 1.3 mm, respectively. The surface area of the plastic package is 6.25 cm\(^2\). The partial pressure difference of oxygen across the package wall is 0.30 atm. The permeability coefficient of oxygen in LDPE and PET are \(4.18 \times 10^{-8} \, \text{cm}^3 \, \text{cm cm}^{-2} \text{s}^{-1}\text{atm}^{-1}\) and \(1.67 \times 10^{-10} \, \text{cm}^3 \, \text{cm cm}^{-2} \text{s}^{-1}\text{atm}^{-1}\), respectively. If the food gets spoiled when it absorbs 0.025 ml oxygen, then the shelf life of food in days is:
Dimensionless numbers play an important role in correlating transfer coefficients during forced convection. In relation to the dimensionless numbers, the correct statement(s) is/are:
The minimum fluidization height of 1.20 m is maintained during fluidized bed drying of carrots. The bed diameter of the fluidized bed dryer is 0.6 m. If mass and solid density of carrots are 250 kg and 1040 kg/m\(^3\), respectively, then the porosity of the bed at the minimum fluidization condition is \underline{\hspace{3cm}} (rounded off to 3 decimal places, \(\pi = 3.14\)).
The microbial death kinetics for a food suspension follows the equation: \[ \log \frac{N_0}{N} = 1 + \frac{t - t_l}{D} \] where \(N_0 =\) initial microbial load, \(N =\) microbial load after time \(t\), \(t_l =\) lag time, and \(D =\) decimal reduction time. The correct statement for this equation is:
The log mean temperature difference (LMTD) correction factor is not required during heat transfer rate calculation in:

In a triple effect feed forward evaporator, pineapple juice is entering at the rate of 6.3 kg s$^{-1}$ and leaving the last effect as 50% concentrate. The system is using saturated steam of 2.48 kg s$^{-1}$ at 121.1°C. If vapour transferred from the first to the second effect, second to third effect and third to ambient are 5675, 6053 and 6416 kg h$^{-1}$, respectively, the steam economy of the evaporator is _____. \(\textit{[Round off to two decimal places]}\)

The ordinates of an inflow hydrograph are provided in the table below. If the routing interval (\(\Delta t\)) is one hour, weighting factor in Muskingham equation (X) is 0.2, and the storage-time constant (time of travel of flood wave through the channel reach) (K) is 0.7 hour, using the Muskingham method of flood routing, the ordinate of the outflow (routed) hydrograph for 2nd hour in m\(^3\) s\(^{-1}\) is _____. \textit{[Round off to two decimal places.]}
A cylindrical metallic silo of 3 m internal diameter and 10 m depth is loaded with maize grain having bulk density of 720 kg m\(^{-3}\). The angle of internal friction between the maize grains is 24°, and that between the grain and wall is 22°. Using Airy’s theory, the calculated lateral pressure in kPa at the bottom of the silo is _____. \textit{[Round off to two decimal places.]}
Energy requirement (E) to produce a change (dX) in dimension X of a particular size can be expressed as \[ \frac{dE}{dX} = - \frac{c}{x^n} \text{ where, } c \text{ is constant and } n \text{ according to Rittinger's law is } \text{__________.} \]