Process Fundamentals · Heat Transfer · Heat Exchangers · Process Equipment
Types of Heat Exchangers: 7 Essential Designs Every Engineer Should Know
A heat exchanger has no motor, no power supply, and no moving parts, yet it quietly does one of the most important jobs in any process plant. This guide explains the types of heat exchangers in plain words, covers both flow based and construction based designs, and gives you a simple heat duty calculator.
What Is a Heat Exchanger?
Heat always moves from a hot object to a cold object when the two come into contact. A heat exchanger is simply the device built to make that happen on purpose, between two separate streams of liquid or gas. It has four ports in total, two for one media and two for the other. Both media flow through, exchange heat across a dividing wall, and leave through their own outlets without ever mixing directly.
There is no pump or motor inside a basic heat exchanger. Once the two flows start moving, the exchange of heat happens on its own through conduction across the wall. Knowing the types of heat exchangers available helps engineers pick the right one for each job, and makes heat exchangers a common partner to control valves, which regulate flow rate to hold the outlet temperature at the desired target.
How a Heat Exchanger Transfers Heat: 4 Steps
The hotter fluid or gas enters its inlet port and begins flowing through its designated path.
→The cooler fluid or gas enters its own separate inlet, staying physically apart from the hot stream.
→Heat naturally moves from the hot side to the cold side through the metal wall that separates them.
→The hot stream leaves cooler, and the cold stream leaves warmer, without the two ever mixing.
Four Common Heat Exchanger Constructions
A bundle of tubes runs inside a larger outer shell. One media flows through the tubes, the other flows around them inside the shell.
Good for: high pressure, high temperature industrial service.
Corrugated plates are stacked together in a frame, with the two media flowing through alternating gaps between plates.
Good for: compact installations needing high heat transfer in a small footprint.
Similar to shell and tube, but one tube runs inside another. One media flows through the inner tube, the other through the space between the two tubes.
Good for: smaller flow rates and simpler installations.
Instead of simply heating or cooling, one media actually changes state, boiling into gas in an evaporator or condensing into liquid in a condenser.
Good for: boilers, evaporators, cooling towers, and condensers.
Cocurrent, Countercurrent and Cross Flow
The 7 Essential Types of Heat Exchangers
Heat Exchanger Duty Formula
Where:
Q = heat duty (energy transferred per unit time)
m = mass flow rate of the media
Cp = specific heat capacity of the media
ΔT = temperature change across the exchanger
Example: Water flow = 2 kg/s, Cp = 4.186 kJ per kg per °C, ΔT = 15°C Q = 2 × 4.186 × 15 = 125.6 kW This is the same basic formula used to size a heat exchanger for a given duty, regardless of whether it is shell and tube, plate and frame, or another construction. The exchanger's actual surface area and flow arrangement then determine how efficiently it can achieve this required heat transfer.
Shell and Tube vs Plate and Frame
Among all the types of heat exchangers, these two construction styles are compared most often when choosing equipment for a new process.
Where Heat Exchangers Are Used
Different types of heat exchangers show up across nearly every industry that moves heat from one fluid to another.
Warm water is cooled while the refrigerant absorbs the heat and warms up.
Hot lubricating or hydraulic oil is cooled before returning to service.
Air is heated or cooled through coils acting as a form of heat exchanger.
Steam is condensed back to water after passing through a turbine.
Reaction heat is removed to keep a chemical process within a safe temperature range.
Plate heat exchangers rapidly heat and then cool liquid food products for safety.
Selecting the Right Heat Exchanger
- Prefer countercurrent flow where possible: it generally achieves better heat transfer than cocurrent flow for the same size.
- Choose shell and tube for demanding service: high pressure and high temperature applications favor its rugged construction.
- Choose plate and frame for tight spaces: when high efficiency in a small footprint matters most.
- Verify flow direction on the P&ID: before startup to avoid an accidental cocurrent setup where countercurrent was intended.
- Don't assume cocurrent and countercurrent perform the same: the flow direction genuinely changes heat transfer efficiency.
- Don't ignore fouling and cleaning needs: deposits building up inside the exchanger reduce performance over time.
- Don't undersize the surface area: for the required heat duty, or the target outlet temperature will never be reached.
- Don't mix incompatible media without checking wall material: corrosive or reactive combinations need the right material selection.
Heat Exchanger Duty Calculator
Enter mass flow rate, specific heat, and temperature change to calculate the heat duty.
Quick FAQs: Types of Heat Exchangers
External References
- Wikipedia: Heat Exchanger
- TEMA: Standards for Shell and Tube Heat Exchangers
- Alfa Laval: Plate Heat Exchanger Reference Guide
What we learn today
- A heat exchanger transfers heat between two separate media through a dividing wall, without the two streams ever mixing.
- The types of heat exchangers split into flow based designs, cocurrent, countercurrent, and cross flow, and construction based designs, shell and tube, plate and frame, double tube, and media conversion.
- Countercurrent flow generally achieves better heat transfer than cocurrent flow for the same exchanger size.
- The basic heat duty formula, Q = m × Cp × ΔT, applies across every construction type and is the starting point for proper sizing.