96 Fermentation and Biochemical Engineering Handbook and then shutting off all cooling. The time interval is then very carefully measured for the broth to heat up to re(△ T and time) b. Assume specific heat of broth= 1.0 Btu/lb-F c. Volume of broth by level indicator (or best estimate) Q3=SpHt. x broth vol.×8345×△T÷ time(hr) 23= Btu/hr 4. Heat Added by Mechanical Agitation a. Determine or assume motor and gear box efficiency about 0.92) 6. Measure kw of motor Q4=kW×3415× efficiency=Btu/hr 5. Heat of Fermentation=AH, g1+Q2+g3-4=MH The heat of fermentation is not constant during the course of the fermentation. Peaks occur simultaneously with high metabolic activity Commercial fermentation is not constant during the course of the fermenta tion. Commercial fermentations with a carbohydrate substrate may have peak loads of 120 Btu/hr/gal. The average AH, for typical commercial fermentations is about 60 Btu/hr/gal. The average loss of heat due to evaporation from aeration is in the range of 10 to 25 Btu/hr/gal. Fermenta tions with a hydrocarbon substrate usually have a much higher AHf than carbohydrate fermentations. Naturally, most c determine the△Hr for each product, especially after each major medium revision. (Typically, data are collected every eight hours throughout a run to observe the growth phase and production phase. Three batches can be averaged for a reliable AHf.) In this manner, the production department can give reliable data to the engineering department for plant expansions96 Fermentation and Biochemical Engineering Handbook and then shutting off all cooling. The time interval is then very carefully measured for the broth to heat up to running temperature (AT and time). b. Assume specific heat of broth = 1 .O BtuAb-OF c. Volume of broth by level indicator (or best estimate) = gal Q3 = Sp.Ht. x broth vol. x 8.345 x AT + time (hr) 4. Heat Added by Mechanical Agitation a. Determine or assume motor and gear box efficiency b. Measure kW of motor (about 0.92) Q4 = kW x 3415 x efficiency = Btuihr 5. Heat of Fermentation = AHf e, + Q2 + Q3 - Q4 = AHf The heat of fermentation is not constant during the course of the fermentation. Peaks occur simultaneously with high metabolic activity. Commercial fermentation is not constant during the course of the fermenta￾tion. Commercial fermentations with a carbohydrate substrate may have peak loads of 120 Btu/hr/gal. The average AHf for typical commercial fermentations is about 60 Btu/hr/gal. The average loss of heat due to evaporation from aeration is in the range of 10 to 25 BtuMgal. Fermenta￾tions with a hydrocarbon substrate usually have a much higher Mf than carbohydrate fermentations. Naturally, most companies determine the AHr for each product, especially after each major medium revision. (Typically, data are collected every eight hours throughout a run to observe the growth phase and production phase. Three batches can be averaged for a reliable AHf.) In this manner, the production department can give reliable data to the engineering department for plant expansions