You work for a surgeon who asks you to design a heat-exchanger device to continu

Question

You work for a surgeon who asks you to design a heat-exchanger device to continuously heat 10 L/min of blood from 5 degree C to 38.8 degree C by transferring heat from warm water. Assuming that the specific heat capacity of blook is 1.4 cal/g. degree C) and its density is constant at 1.3 g/mL, estimate the required rate of heat transfer in J/min. In addition, to achieve the same goal, blood can be warmed by flowing through coils that are immersed in a large water bath. The initial temperature of the water bath is 60 degree C and no more heat is supplied to the water bath. The surgery lasts 3 hours and the final water temperature should not fall below 35 degree C. Determine the necessary volume of the water bath and commend on its feasibility as well as ways to improve it.

Explanation / Answer

Heat transfer

Q=mcpT

m=mass flow rate=density*volumetric flow rate=1.3*103 gm/lit*10 L/min=1.3*104 gm/min

cp=1.4 cal/g0C

So

Q=1.3*104*1.4*(38.8-5)=615160 cal/min=615160*4.184 J/min=2573829.44 J/min

Now heat gain by water=Heat gain by blod=2573829.44 J/min

specific heat of water=4.184 J/g 0C

So

2573829.44 =m*4.184*(60-35)

m=24606.4 gm/min

water density =1 gm/ml

So V=24606.4 ml/min

If surgery time= 3 hr=3*60=180 min

volume=4429152 ml=4429.152 lit

2573829.44 =m*

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