The surface tension of water, a needed quantity in several of the following problems, is related to temperature according to the expression = 0.1232[1 − 0.00146 t], where is in n/m and t is in k. in the english system with given in ⁄ ft t in ℉, the surface tension may be calculated from = (8.44 × 10−3)[1 − 0.00082 t]. 1. water flowing at rate of 4000 kg/h through a 16.5-mm-id tube enters at 20℃. the tube outside diameter is 19mm. saturated atmospheric steam condenses on the outside of the tube. for a horizontal brass tube 2 m long, evaluate a) the convective coefficient on the water side. b) the convective coefficient on the condensate side. c) the exit water temperature. d) the condensation rate.

Amass of m 1.5 kg of steam is contained in a closed rigid container. initially the pressure and temperature of the steam are: p 1.5 mpa and t 240°c (superheated state), respectively. then the temperature drops to t2= 100°c as the result of heat transfer to the surroundings. determine: a) quality of the steam at the end of the process, b) heat transfer with the surroundings. for: p1.5 mpa and t 240°c: enthalpy of superheated vapour is 2900 kj/kg, specific volume of superheated vapour is 0. 1483 m/kg, while for t 100°c: enthalpy of saturated liquid water is 419kj/kg, specific volume of saturated liquid water is 0.001043m/kg, enthalpy of saturated vapour is 2676 kj/kg, specific volume of saturated vapour is 1.672 m/kg and pressure is 0.1 mpa.

The mass flow rate of the fluid remains constant in all steady flow process. a)- true b)- false

Which of the following components of a pid controlled accumulates the error over time and responds to system error after the error has been accumulated? a)- proportional b)- derivative c)- integral d)- on/off.