99年化工原理期末考试题.doc

Final Examination for Unit Operations of Chemical Engineering Grade 99，2001/12/25 Name Student No. Class Score (45 points) True or false or fill the black or choose the correct answer ( ) In a laminar flow, the frictional coefficient (Fanning Factor f) is inversely proportional to Re. ( ) At heat transfer by conduction, q (heat flow rate) is always constant. ( ) When a fluid passes through a pipe, the total mechanical energy in section 1 (inlet) is always equal to that in section 2 (outlet). ( ) When the inlet and outlet temperatures are fixed, LMTD (logarithmic mean temperature difference) is always larger than that of arithmetic mean temperature. ( )When the developed head H is the same, one pump can develop more volume flow rate than that two same pumps which work in parallel. The orifice meter belongs to , flow rate meter; while the rotameter is , flow rate meter. A) constant pressure drop; B) constant area; C) variable pressure drop; D) variable area There are often two kinds of condensation processes in industry, which are (1) ; (2) , respectively. ( ) If the inlet and outlet temperatures of fluids are fixed, the LMTD of countercurrent flow is always larger than that of parallel-current flow without phase heat transfer. In order to avoid the cavitation, the following is feasible. increase the operating temperature; decrease the diameter of suction pipe; install the valve or fittings in the suction pipeline; reduce the frictional loss in the suction pipeline (10) The expression of Newton’s Cooling law is ( ). (11) The orifice meter is used to measure ; the rotameter is utilized to measure ; the Pitot tube is used to measure average velocity in the orifice; volume flow rate in the orifice; average velocity in annular space between the float and tube wall; volume flow rate in annu