Question

Saturated steam at a pressure of 2 bar is to be used to heat a stream of ethane. The ethane enters a heat exchanger at 16ºC and 1.5 bar at a rate of 795 m3 /min and is heated at constant pressure to 93ºC. The steam condenses and leaves the exchanger as a liquid at 27ºC. The specific enthalpy of ethane at the given pressure is 941 kJ/(kg.oC) at 16ºC and 1073 kJ/(kg.oC) at 93ºC

a) Draw a flow diagram and do a degree of freedom analysis for this problem.

b) How much energy (kW) must be transferred to the ethane to heat it from 16ºC to 93ºC? (Write the energy balance and list all assumptions.

c) Assuming that all the energy transferred from the steam goes to heat the ethane, at what rate in m3 /s must steam be supplied to the exchanger? If the assumption is incorrect, would the calculated value be too high or too low? (15 pts) d) Should the heat exchanger be set up for co-current or counter-current flow? Explain

Answer 1

Ethane 795mmin 16 C .5 bar Conduysed Liquid 2 7C Sud- Steam 2 baY Ethane,5 mnin sbar, 93'c. b Heat released by ateanm to condsee Heat aained by Hat tnanfuud h aaa 16:C= 1973_KI/ng 132५3/&g- ehthaleyat 93(- otalyat 941kt/g 745 Vnlusaaiclow of elaoasas 95 m3/min = = 13-25ms Deaiyof ethesae = 125324 kg/3 So Mass Aow nade 13.25 ms y25324 Kg/3 16.6054g/s So Cauna^_liens fered = 132 Ks/kgy l6i 6o541 211.912g Kw Asausagliaaa ty nemaana Cst taeuneat i Ne Pressune dnep change in aadtaalay = chacage in tasat C No oxtual eonk d Fon ean at 2 bar nthalp 2710 K1/k Cfnom propent cdaat Assassoring the exi Aiguioh to be aabunaded Iiguid a 2e aabexib- 13Kg damage in eanaudpyz2710-113)= 2591 KJ/Kg. Mas Apu ofwalen negpainsel - 2191. 9128 K J/S : 0-१4१ /k Nome low nale -9f asg hon ig lncorwset calcasdad ed vodne w/1 be taelarg d ay pnesered to uwe Condencreatbaeab exchacgen becaus thtepenatunedifterafebchuan th hat cold streasrema inear. Aut ncase of cercurrud lar reacapenakuragadind vwaies abnen alng Hee 9lelaasaterhanger ০৪५५w७/s Tooo