السلام عليكم ورحمة الله وبركاته

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أنا عضو جديد في هذا الملتقى ولم استطع حل هذه المسأله لانه يوجد لدي لبس في فهم اساسيات في هذه الماده(Heat Transfer) والمسأله كما يلي:

Hot air for a large-scale drying operation is to be produced by circulating the air over a tube bank (unmixed), while products of combustion (exhaust gas) are circulated inside the tubes. The surface area of the cross-flow heat exchanger is A = 25 m2, and for the proposed operating conditions, the manufacturer specifies an overall heat transfer coefficient of U = 35 W/m2·K. The air and the combustion gases may each be assumed to have a specific heat of cp = 1040 J/kg·K. Consider conditions for which combustion gases flowing at 1 kg/s enter the heat exchanger at 800 K, while air at 5 kg/s has an inlet temperature of 300 K.

1. Determine the outlet and gas temperatures?
2. After extended operation, deposits on the inner tube surfaces are expected to provide a fouling resistance of 0.004 m2 K/W. f R′′ = how this will affect the heat
exchanger performance?
3. The heat exchanger performance can be improved by increasing the surface area
and/or the overall heat transfer coefficient. Explore the effect of increasing the

product (UA) on air outlet temperature for the range 500 UA 2500 W K.


انا وضعت هذه المسأله بين أيديكم لكي اتمكن من الاستفادة من ذوي الخبرة في حلها والاستفاده من الشروحات لكي اصحح ماعندي من قصور في فهم الاساسيات.

ودمتم بود