## A Simple Method to Evaluate Heat Exchanger Performance

In this post, I want to share a simple method to evaluate heat exchanger performance. One of the most helpful ways to evaluate the performance of heat exchanger is to determine its effectiveness by comparing the actual heat transfer rate to the maximum rate that is thermodynamically feasible. The simple formula is expressed below.

Where:

η        = effectiveness

Q       = actual heat transfer rate

Qmax    = heat transfer rate which would be achieved if it were possible to bring the exit temperature of the stream with the lower heat capacity, to the inlet temperature of the other stream. Read More

## How to Estimate Time Required for Heating or Cooling

In this post, I want to share how to estimate time required for heating and cooling.

The contents of a large batch reactor or storage tank frequently need to be heated or cooled. In this circumstance, the physical properties of the liquor may change throughout the process, as well as the overall transfer coefficient. When estimating the amount of time needed to heat or cool a batch of liquid, it is frequently possible to assume an average value for the transfer coefficient. Steam condensing, either in a coil or some type of hairpin tube heater, is a common method for heating the content of storage tank.

It is reasonable to assume that the overall transfer coefficient U is constant in the context of a storage tank filled with liquor having mass m and specific heat Cp and heated by steam condensing in a helical coil. The rate of heat transfer is given by: If T s is the temperature of the condensing steam, T1 and T2 are the initial and final temperatures of the liquor, A is the area of the heat transfer surface, and T is the temperature of the liquor at any time t, then:

The time t for heating from T1 to T2 can be determined using this equation. If the steam condenses in a reaction vessel’s jacket, the same analysis may be applied.

Heat losses during the heating or, for that matter, cooling operation are not considered in this analysis. The heat losses increase naturally as the temperature of the vessel’s contents rises, and at a certain point, the heat supplied to the vessel equals the heat losses, making further increases in the temperature of the vessel’s contents impossible.

By increasing the rate of heat transfer to the fluid, for example, by agitating the fluid, and by minimizing heat losses from the vessel by insulation, the heating-up time can be shortened.

The amount of agitation that can be achieved in a large vessel is constrained, thus one attractive alternative is to circulate the fluid through an external heat exchanger.

Let’s see example below on how to estimate time required for heating or cooling. Read More

## Design of Air-Cooled Exchanger (Part 1)

Air-cooled exchangers are used to cool fluids with ambient air. They should be considered when cooling water is in limited or expensive. Air-cooled exchangers are used for cooling and condensing.

Air-cooled exchangers consist of banks of finned tubes over which air is blown or drawn by fans mounted below or above the tubes. Air-cooled exchangers are classified as forced draft when the tube section is located on the discharge side of the fan, and as induced draft when the tube section is located on the suction side of the fan. Read More

## Design of Shell and Tube Heat Exchanger – Tube Side Construction

In my previous post, design of shell and tube heat exchanger – layout design, I shared how to select fluid allocation, which one should be in tube side and which one should be shell side, general rule for allowable fluid velocity, pressure drop, and temperature approach. This post will be the continuation of design of shell and tube heat exchanger series, which specifically explain about construction detail in tube side.

Want to learn from the beginning?
Read my first post about step-by-step design of shell and tube heat exchanger. Still curious? Read my second about about layout design of shell and tube heat exchanger.

This is mind map of this topic.

## Design of Shell and Tube Heat Exchanger – Layout Design

In my previous post, I share about step-by-step design of shell and tube heat exchanger. In this post I want to share you specifically about exchanger layout design. This layout design consists the following items.

## Design of Shell and Tube Heat Exchanger

It’s been quite a long time since the last time I saw and designed shell and tube heat exchanger. Recently, I got opportunity to dig and refresh knowledge that type of heat exchanger. In this post, I want to share you about design of shell and tube heat exchanger.

This figure shows you general step-by-step method of design of shell and tube heat exchanger.

## Heat Loss Calculation of Tank Heater

My recent study was to calculate heat loss in tank heater in order to determine condensate load. It was a pretty simple method. In this post, I provide you the example of my calculation and I hope you find it useful. The problem statement was:

1. Heat marine fuel oil from 50 to 60 degree C in 5 hours
2.  Continue to maintain 60 degree C in an insulated tank with a wind velocity 10.08 km/h and an ambient temperature of 27.4 degree C
3. Tank is 6.8 m diameter and 6.04 m of height
4. Steam is available at 8 barg

You can find the source of my calculation from this link.