Q1: A process stream of dilute aqueous solution flowing at the rate of10 Kg.s^-1 is to be heated. Steam condensate at 95°C is available for heating purpose, also at a rate of 10 Kg.s^-1. A 1 - 1 shell and tube heat exchanger is available. The best arrangement is

ANS:A - counter flow with process stream on shell side.

To determine the best arrangement for the heat exchanger, we need to consider the temperature profiles of the process stream and the steam condensate, as well as the desired outcome of the heating process. Given that the steam condensate is at 95°C and the dilute aqueous solution needs to be heated, it's clear that we want the highest possible temperature difference between the two fluids to maximize heat transfer efficiency. For this purpose, counterflow arrangement is typically the most efficient. In a counterflow arrangement, the hot fluid (steam condensate in this case) enters from one end of the heat exchanger while the cold fluid (dilute aqueous solution) enters from the opposite end. This allows for the highest possible temperature difference between the two fluids along the length of the heat exchanger, leading to efficient heat transfer. Now, we need to decide which fluid should flow through the tubes and which should flow through the shell. Typically, the fluid with the higher heat capacity or the one that requires more heating should flow through the side with more surface area available for heat transfer, which is usually the shell side in a 1-1 shell and tube heat exchanger. In this case, the steam condensate at 95°C has a higher temperature and higher heat capacity compared to the dilute aqueous solution. Therefore, it's preferable to have the steam condensate flowing through the shell side and the dilute aqueous solution flowing through the tube side. So, the best arrangement would be "counterflow with process stream on tube side."