Question

Cold water (cp= 480J/kg c) leading to a showen entors thin- walled double-pipe counter How heat exchanger at 15°c at of 0.28 kg/s and is heated to 45° c by hot water (cp= 4190 g J/kg) that enters at 100c at rate of 3kgls. If owall heat transfer coefficient is a 950 W/m² °C. Dotermine rate of heat transfer and heat transfer surface area of heat exchanges using E-NTU method​

Answer 1

COLD  WATER   STREAM 

 Mwc  = cold  water  mass flow rate = 0.25 kg/s

Cpcw  = specific heat   of cold water  = 4180 j /kg-k 

  cold  water   inlet temperature  = Twci=  15  oc 

   cold  water   outlet temperature = Two  =45 oc  

  heat gained  by cold water  = Qwc  = Mwc*Cpcw* ( Two  - Twi)  =  0.25 * 4180 * (45-15 ) =   31350 j /s  =  31350 W 

  Mwhw  =  mass   flow  rate   of hot water  =  3 kg/s  

 Cpwh  = sp.  heat of hot  water  =4190  j/kg -k 

 inlet   water   temperature  = Thi = 100  oc  

 out...