electric fan system the temperature of the air stream is as follows u03b4 t fan 5 2 u00d7 pr density u00d7 c p u00d7 778 a constant to balance units u00d7 efficiency fan u00d7 efficiency motor wherein pr pressure rise across the fan of 1 02 is converted into inches of water 1 psi 27 7 in h 2 o cp specific heat at constant pressure is 0 24 for air density at sea level in lb cu ft is 0 0765 for air efficiency fan is assumed to be 80 and efficiency motor is assumed to be 80 therefore exit air stream temp ambient temp u03b4 t fan 28 u00b0 f 4 63 u00b0 f 32 63 u00b0 f for the present invention the exit air stream temperature is a combination of the temperature and mass of the fan flow with the temperature and mass of the turbine flow as follows efficiency of the fan was 69 since there is no motor motor efficiency does not enter into the equation wherein y pr 283 u2212 1 pr pressure drop across turbine is 115 15 or 7 67 efficiency turbine is 45 and t in is in degrees rankine 35 u00b0 f 460 495 u00b0 r thus for a tip turbine fan to achieve power balance the mass flow of the turbine is 3 65 lbs min vs the fan flow of 68 8 lbs min therefore exit air stream temp w turb u00d7 t turb u00b0 r w fan u00d7 t fan w tot u2212 460 wherein t turb equals u2212 62 6 u00b0 f 35 u00b0 f u2212 97 6 u00b0 f or 397 4 u00b0 r t fan equals 32 29 u00b0 f 28 u00b0 f 4 29 u00b0 f or 492 3 u00b0.