Dairy and Food Engineering - Agricultural Engineering Previous Year Questions

A refrigeration system based on reverse Carnot cycle operates between −30 °C and 20 °C. The refrigeration capacity of the system is 70 kW. Heat rejected at the condenser to atmosphere (hot reservoir), in kW, is nearest to

A 2 mm diameter electric wire is insulated with 2 mm thick plastic. The plastic has a thermal conductivity of 0.5 W.m^-1.K^-1. The wire is exposed to air at 320 K and outside convective heat transfer coefficient is 25 W.m^-2.K^-1. Wire surface temperature is constant at 420 K and remains unaffected by the covering. Assuming steady state heat transfer conditions, the ratio of heat loss per metre of wire length with insulation to that without insulation is nearest to
(Take π = 3.14)

Pasteurisation of milk can be carried out either at 91 °C for 3 s or at 73 °C for 30 s to inactivate vegetative cells of microorganism(s). The sterilisation value is 10 in both the cases. Thermal death time constant (z value) for reference temperatures of 73 °C and 91°C, in °C, is nearest to