The figure shows a schematic of a system used to generate su

The figure shows a schematic of a system used to generate superheated steam at 50 bar. The system is powered by propane fuel, fed from a conventional LPG tank maintained at 25 degree C When full, the tank stores 400 gal of the saturated propane liquid To fuel the heating system, saturated propane gas from the upper space of the tank is throttled to I bar before being fed the superheater at a flowrate of 30 SLPM. Here the fuel completely combusts with 60% excess air. After throttling, heal transfer with the ambient surroundings warms back the propane to 25 degree C Take all flows in the system as isobaric and assume that no energy escapes the system as work or heat You are encouraged to use appropriate computational tools such as Excel or Matlab for this assignment Explain the meaning of unit SLPM. What quantity does it measure\'? Clearly explain What is the flowrate of propone into the system? Answer in both kg/s and mol/s. what is the flowrate of air in the system? Answer in and mol/s. How long will it take for all the propane liquid to Ieave the tank?

Solution

Answer:

a) SLPM is the abbrevation for Standard Litres Per Minute.

It is a standard measure for the volumetric flow rate of a gas corresponding to the standard conditions of temperatutre and pressure.

It can be converted into SI units using the formula given below.

b) The flowrate of propane is given as 30 SLPM = 30 * 1.68875 / (1*10⁵) = 50.6625 m³ / s

to convert m³ / s to kg / s we have to multiply by density ( kg/m3)

the density of propane is 2 kg /s .

therefore the flowrate of propane is 50.6625 * 2 = 101.325 kg/s

to convert kg/s to mol/s , divide flowrate by molecular weight

the molecular weight of propane is 44 g / mol = 44 * 10^-3 kg/mol.

hence the flowrate of propane in mol / s = 101.325 / (44 * 10^-3) = 2302.8 mol / s

d) the amount of propane liquid in the tank is 400 gal

1 gal = 3.78541 litres therfore 400 * 3.78541 = 1514.16 litres

flowrate is given as 30 litres/ min

therefore time taken to drain all the propane liquid is 1514.16/30 = 50.47 minutes.