Question

The heat exchanger in a heat lung machine is constructed so that blood flows through an array of tubes controlled temperature water circulated through an outer exterior shell.

e heat exchanger in a heat lung machine is constructed so that blood flows through an array of tubes with controlled temperature water circulated through an outer exterior shell. Although the temperature of the blood varies as it passed through the heat exchanger, during the cool down cycle when a patient is being brought to a state of hypothermia in preparation for heart surgery, the average temperature difference between the blood and water within the heat exchanger is targeted to be 17°C. The effectiveness of the heat exchanger is d number of factors including the convective heat transfer coefficients between the blood and water and adjacent walls of the tube, plus the thermal conductivity and geometry of the tube. Given the following specific operating conditions: the inner diameter of the heat exchanger tubing is 10 mm, and the wall thickness is 1 mm; the materials of the tubing is 304 stainless steel, which has a thermal conductivity 3. Th 9 W/(mK); the convective heat transfer coefficient on the interior of the tube of 14. is 750 W/(m2K) and on the exterior is 2,250 W/(m2K) (a) Determine the average heat flow per unit surface area of the heat exchanger. (b) As a further design consideration, it is proposed to alter the design of the heat exchanger by substituting tubing fabricated from treated aluminum alloy with a thermal conductivity of 175 W/(mK). How do you predict this change will affect the performance of the heat exchanger?

Answer 1

In (Pn) 1 Considor lorgth of im Us: 472.17 4 w/m? MTK. Heat flux : ha at fluo -Us AT 4 72.174 x 17 = 18.0 27kW un change th co KA