Exergetic Analysis and Exergy Loss Reduction in the Milk Pasteurization for Italian Cheese Production

Abstract

The cheese industry has high energy consumption, and improvements to plant efficiency may lead to a reduction of its environmental impact. A survey on a sample of small-medium Italian cheese factories was carried out in order to assess the efficiency of heat recovery of the milk pasteurization equipment for the cheese production. Then, an exergetic analysis to calculate the related exergy loss was carried out together with a cost-benefit analysis to identify the optimized value of the heat efficiency. The exergy loss reduction was determined throughout an exergy analysis that takes into account this last value and the comparison with the previous exergy losses. Finally, the feasibility and the consequent additional reduction of exergy losses were verified, if a cogeneration heat and power (CHP) combined to the pasteurization equipment is assumed. Results show a current heat recovery efficiency of 93.2% in the Italian cheese factories; a close connection between the exergetic losses and the efficiency of the heat recovery exchanger; the optimized recovery efficiency equal to 97.3% obtained from the cost-benefit analysis; a related important exergetic loss reduction of −45% in the heat exchangers, as a second result of the exergetic analysis; a similar reduction of the exergy loss (−42%) of the whole system, as a third result of the exergetic analysis; a total exergy loss reduction of 22.9 kJ kg−1milk, which corresponds to a lower environmental impact due to CO2 reduction; a further reduction of the exergy loss of −10% when the cogeneration heat and power CHP are used.

Conveyor-Belt Dryers with Tangential Flow for Food Drying: Development of Drying ODEs Useful to Design and Process Adjustment

“…This one, T P , was assumed to be equal to the wet bulb temperature T WB . The infinitesimal heat transfer rate dq, transmitted from the air [64][65][66] to the product through the infinitesimal area dA, as shown in Figure 2, can be written as follows: = ⋅ ⋅ − ; where: α is the convective heat transfer coefficient; dA is the infinitesimal area; TA is the air temperature when it comes into contact with the area dA; TWB is the product temperature, assumed to be equal to the wet bulb temperature of the air.…”

“…Therefore, the TPI = TWB assumption was acceptable. The infinitesimal heat transfer rate dq, transmitted from the air [64][65][66] to the product through the infinitesimal area dA, as shown in Figure 2, can be written as follows:…”