How do you detect fouling in a heat exchanger?
How do you detect fouling in a heat exchanger?
How to detect fouling in heat exchangers
- Temperature transmitters. Monitor the temperature of fluids passing through heat exchangers.
- Pressure transmitters. Detect pressure drops between heat exchanger inlet and outlet.
- Flow Meters. Indicate decreases that may be caused by build-up of fouling material in pipes and plates.
What are the different types of fouling in heat exchangers?
Types of fouling
- Precipitation fouling. It is scale formation on heat transfer surface due to dissolved substances like CaCO, Caso, salts present in water result in precipitation fouling.
- Particulate fouling.
- Chemical reaction fouling.
- Corrosion fouling.
- Biological fouling.
- Solidification fouling.
What are the methods for analyzing heat exchangers?
Heat exchangers are usually analyzed using either the Logarithmic Mean Temperature Difference (LMTD) or the Effectiveness – Number of Transfer Units (ε-NTU) methods. The LMTD method is convenient for determining the overall heat transfer coefficient based on the measured inlet and outlet fluid temperatures.
Which method is used for heat exchanger?
The main methods of heat exchanger design and analysis are those of the logarithmic mean temperature difference (LMTD) method and the effectiveness (ɛ) number of transfer units (e-NTU) method, with the latter being used for detailed application here.
What are the common causes of fouling in a heat exchanger?
The most common definition of fouling in relation to heat exchangers is the deposition and accumulation of unwanted material such as scale, suspended solids, insoluble salts and even algae on the internal surfaces of the heat exchanger.
What is difference between scaling and fouling?
Scaling is a type of fouling caused by inorganic salts in the water circuit of the heat exchanger. It increases the pressure drop and insulates the heat transfer surface, thus preventing efficient heat transfer. The salts are therefore deposited on the warm surface when the cold water makes contact with it.
What are the fouling factors?
The fouling factor represents the theoretical resistance to heat flow due to a build-up of a layer of dirt or other fouling substance on the tube surfaces of the heat exchanger, but they are often overstated by the end user in an attempt to minimise the frequency of cleaning.
How do you minimize fouling?
The best way to avoid particulate fouling is to keep the cooling water clean and thereby prevent particles from entering the heat exchanger. However, in all cooling systems, and especially when using open cooling systems (with cooling towers), there will always be particles present in the cooling water.
Why LMTD is used in heat exchanger?
The log mean temperature difference (LMTD) is used to determine the temperature driving force for heat transfer in flow systems, most notably in heat exchangers. The LMTD is a logarithmic average of the temperature difference between the hot and cold streams at each end of the exchanger.
How do you build a good heat exchanger?
For the sizing problem:
- Calculate the effectiveness.
- Calculate the capacity rate ratio.
- Calculate the overall heat transfer coefficient.
- Determine NTU.
- Calculate the heat transfer surface area.
- Calculate the length of the tube or heat exchanger.
What is the purpose of baffles in heat exchanger?
Baffles serve two functions: Most importantly, they support the tubes in the proper position during assembly and operation and prevent vibration of the tubes caused by flow-induced eddies, and secondly, they guide the shell-side flow back and forth across the tube field, increasing the velocity and the heat transfer …
What is the procedure of removing fouling from heat exchanger?
Deposition fouling is normally removed mechanically by brushing or scraping. Corrosion fouling occurs when a layer of corrosion products builds up on the surfaces of the tube, forming an extra layer of material that often has thermal resistance.
How is fouling detected in a heat exchanger?
Investigated methods for fouling detection are e.g. weighing of fouled and clean tubes and plates of heat exchangers ( Burton, 1961, Tissier and Lalande, 1986 ), observing disturbances in hydrodynamics ( Corrieu, Lalande, & Ferret, 1986 ), or using heat transfer parameters as fouling indicator ( Davies et al., 1997, Ling and Lund, 1978 ).
Can a pressure drop be used to detect fouling?
This method is standard and can be used as input for other methods e.g. as input in an artificial neural network (ANN) for fouling detection in a plate heat exchanger (PHE) ( Riverol & Napolitano, 2005 ). Usually, pressure drop is measured accompanying to other methods like temperature measurements.
How does backflushing work in a heat exchanger?
Backflushing employs a valve that reverses the flow of fluids through the heat exchanger to force out particulates at the exchanger inlet. A port filter prevents particles from even entering the unit to reduce the amount of fouling. This guide is designed for processors]
Why do you need to clean a heat exchanger?
Heat exchanger cleaning Cleaning is required to maintain heat exchanger efficiency. Cleaning-In-Place (CIP) equipment circulates cleaning chemicals and rinses to flush interior surfaces of heat exchangers without disassembling them. Importance of flow rate during cleaning