Focus: Heat exchangers

Heat exchangers sit at the core of every petrochemical facility, and represent a market segment projected to cross US$12.7 billion by 2012. Petrochemicals Middle East investigates the systems available, and how to find the model best suited to your budget.

Heat exchangers are devices specifically designed for the efficient transfer of heat from one fluid to another over a solid surface. This transfer of heat can either take the form of absorption or dissipation of heat. Heat exchangers can be found in everyday equipment from boilers, furnaces, refrigerators to air conditioning systems.

The exchangers used transfer heat from one liquid to another, without allowing them to mix. The exchange can be to alter the temperature, or state of liquids, either condensing or boiling as required.

Regardless of the function the heat exchanger fulfills, in order to transfer heat the fluids involved must be at different temperatures and they must come into thermal contact, as heat can flow only from the hot to cold, thus the heat is transferred via a metal plate isolating the two fluids.

Heat exchangers are found in most chemical, electrical or mechanical systems and they serve as the system’s means of gaining or rejecting heat. Some of the more common applications are found in heating, electronic equipment, ventilation and air conditioning (HVAC) systems, radiators or internal combustion engines, boilers, condensers and gas preheaters.

http://arabianoilandgas.com/article-5272-focus_heat_exchangers/

Giant plate heat exchangers enlarge the range

Alfa Laval reports that the new T50 model is the largest plate heat exchanger it has ever built, standing 4.5 metres high, weighing 30 tonnes and with a flow rate capacity of up to 975kg/second

Alfa Laval says its new T50 model is the largest Plate Heat Exchanger it has ever built.

Standing 4.5 metres high, weighing 30 tonnes and with a flow rate capacity of up to 975kg/second, the monster unit is ideal for central cooling systems in petrochemical refineries, chemical plants and off-shore oil and gas platforms.

In common with all Alfa Laval Plate Heat Exchangers, the T50 consists of a pack of plates stamped with a special pattern which, once assembled, form channels through which two fluids flow in counter-current to each other, exchanging heat in the process.

The corrugations reinforce the plate structure against differential pressures and also promote turbulence in the fluids.

This, in turn, increases heat transfer efficiency and also serves to inhibit scaling and fouling on the channel walls.

The T50 has a new plate system that improves heat exchanger performance for large cooling requirements.

The system enables three basic plates (low-theta, medium-theta and high-theta) to be combined in five different channel arrangements for specific temperature programmes.

The T50 can be supplied with plates in stainless steel or titanium, nitrile or EPDM gaskets and with connections to DIN or ASME standards.

Each plate provides 3.5 m2 of heat transfer surface meaning a complete unit can provide a massive 2880 square metres of heat transfer surface.

In addition, the exchanger portholes are 500 mm diameter, making it ideal for the cooling of large industrial processes.

http://www.processingtalk.com/news/alv/alv111.html

TLC For Your Furnace - Avoiding Premature Failure of Heat Exchangers

Ever notice how your car seems to run better right after an oil change, especially if you wash and wax it? Well, it's the same for your furnace... don't laugh, I'm serious!

The main component of heating units, both forced air and hot water, is the heat exchanger. This component takes the heat produced by burning fuel and transfers it to the water or air for distribution throughout the house. In a hot water system this component is usually concealed from view, and in a forced air unit only 10 to 25% (sometimes it's completely hidden) of this component is typically visible without disassembly.

Cut-away view of a modern forced-air gas furnaceModern forced-air gas furnace:

1. Solid-state furnace control (Fan assembly visible at lower rear)

2. Draft inducer (fan-forced exhaust)

3. Igniter and flame sensor

4. Gas valve and manifold

5. Gas burners

6. Heat exchanger(s)

7. Air filters

(Configuration will vary between models)

What usually makes heat exchangers inoperative is developing a hole or a crack that allows the hot water to escape, or exhaust from the combustion fuel to escape into the interior air of the home. Constant heating and cooling from years of use will eventually cause a heat exchanger to crack, however some last longer than others. Under ideal conditions, many survive well beyond their predicted life spans.

It seems regular cleaning and maintenance play a factor in life expectancy, as does the environment surrounding the unit. Damp environments tend to assist the build-up of rust on the heat exchanger, shortening its life, while dry, clean environments tend to increase the life span of most furnaces.

Reduced airflow...

Dirty air filters and fan blades, dirty ductwork and obstructed air vents can all contribute to wear on fan motors, reduced efficiency and even premature failure of heat exchangers. Fuel-fired forced-air furnaces are prone to overheating due to obstructions to airflow. Modern furnaces are designed to shut down if temperatures become dangerously high... however, moderately elevated internal temperatures caused by dirt, dust and debris may not be high enough to switch off a furnace, while remaining high enough to cause metal fatigue over extended periods of time.

An annual internal inspection by a licensed burner mechanic or gas fitter, including cleaning and testing for exhaust leaks, should cost between $50 and $100. Considering the implications, I'd say that's a real bargain! Why not have your furnace inspected, and treat yourself to some peace of mind? For those of you with gas furnaces or wood stoves, a carbon monoxide (CO) detector ($30-$45) is an inexpensive means of protection against the possibility of exhaust leaks, between inspections.

http://ezinearticles.com/?TLC-For-Your-Furnace---Avoiding-Premature-
Failure-of-Heat-Exchangers&id=99698

Easiheat system replaces heat exchangers

A single Easiheat engineered system from Spirax Sarco has replaced two bulky shell-and-tube heat exchangers at Abbott Murex's site in Dartford.

The change has delivered reduced maintenance and more space in the plant room.

Abbott Murex is a subsidiary of Chicago-based Abbott Laboratories and produces diagnostic tests designed to protect the blood supply from infectious agents.

The Easiheat system uses plant steam to produce on-demand domestic hot water for sinks and showers throughout the Dartford site.

'The two shell-and-tube heat exchangers were 25 years old and were starting to develop leaks,' says Abbott Murex's engineering facilities manager, Peter Phillips.

'They also took up a lot of space and were difficult to maintain.' The old exchangers also suffered periodically from a build-up of scale and had to be completely stripped down for insurance inspections every other year.

The steam-to-hot-water plate heat exchanger at the heart of the Easiheat system presents no such problems.

'We initially thought we needed to buy two Easiheats, but after talking to Spirax Sarco, we decided that this unit is robust enough and sufficiently easy to maintain for us to rely on just one,' says Phillips.

'That made it a very cost-effective option.' The company purchased a spare set of heat exchanger plates and gaskets at the same time as the Easiheat system itself.

This means that in the unlikely event of a leak or blockage occurring within the exchanger, engineers should be able to fix the problem and have the unit up and running again within an hour.

However, there hasn't been a single problem with the Easiheat unit since it was installed almost a year ago.

http://www.engineeringtalk.com/news/spx/spx166.html

Tranter Heat Exchangers expand range of gasket and welded heat exchangers

Tranter’s range of gasketed plate heat exchanger products are built on a module-based concept supporting combinations of connections, plates and frames from a number of different types of exchangers.

Tranter heat exchangers are able to be easily dismantled for maintenance, inspection and cleaning. Plates are able to be easily added or replaced, supporting changed conditions and easy expansion and adaptation.

The company’s range of welded plate heat exchangers are designed for compact applications in extreme pressures and temperatures that surpass the capabilities of a gasket solution. The plates are small in size and require minimal maintenance.

Tranter welded plate heat exchangers are able to handle two-phase mixtures, gases and liquids, and all at low and high temperatures and high pressure.

http://www.ferret.com.au/c/Tranter-Heat-Exchangers-Former-Swep/Tranter-Heat-Exchangers-expand-range-of-gasket-and-welded-heat-exchangers-n828597

Tranter Heat Exchangers expand range of gasket and welded heat exchangers

Tranter’s range of gasketed plate heat exchanger products are built on a module-based concept supporting combinations of connections, plates and frames from a number of different types of exchangers.

Tranter heat exchangers are able to be easily dismantled for maintenance, inspection and cleaning. Plates are able to be easily added or replaced, supporting changed conditions and easy expansion and adaptation.

The company’s range of welded plate heat exchangers are designed for compact applications in extreme pressures and temperatures that surpass the capabilities of a gasket solution. The plates are small in size and require minimal maintenance.

Tranter welded plate heat exchangers are able to handle two-phase mixtures, gases and liquids, and all at low and high temperatures and high pressure.

http://www.ferret.com.au/c/Tranter-Heat-Exchangers-Former-Swep/Tranter-Heat-Exchangers-expand-range-of-gasket-and-welded-heat-exchangers-n828597

Aptiv film enhances Makatec heat exchangers

Victrex has reported that by replacing metal in its spiral plate heat exchangers with Aptiv film, Makatec has been able to enhance the exchanger's design and reduce overall systems cost.

Heat exchangers are used to transfer heat between fluids and gases.

They can also be used as condensers and evaporators.

In this design, Aptiv film is spiral bound with high-temperature-resistant glue to provide the right mixture of high-temperature performance and chemical resistance.

It provides an effective barrier against many liquids and gases, is lightweight, halogen-free, and withstands lead-free soldering process temperatures.

It is also RoHS compliant and can be used to manufacture products compliant with the same directive.

Environmentally friendly and 100 per cent recyclable, Makatec heat exchangers achieve heat transfer coefficients in the range of 1kW/m2K (176 BTU/hft2F) comparable to conventional plate heat exchangers.

The spiral design allows volume specific heat exchange areas up to 1000 m2/m2 (305 ft2/ft2).

The smooth surfaces of Aptiv film reduce the risk of residue build-up inside the heat exchanger, therefore minimising the danger of microbial contamination.

The heat exchangers are well suited for use in potable water systems and in the food sector, as well as in pharmaceutical industry and biotechnology applications.

By using Aptiv film to replace metal, Makatec has been able to achieve overall systems cost reduction.

The exchanger's simple design allows for low cost assembly even for unique specifications.

It costs less than a stainless steel exchanger and, when compared to conventional plate heat exchangers, operational costs are reduced due to the minimal pressure drop required by the pump engine.

Maintenance and service costs are also reduced due to the corrosion resistance of the Aptiv film.

Aptiv film offers the performance properties of Victrex Peek polymer, including: high temperature capability, chemical resistance, durability and scratch resistance, radiation resistance, mechanical properties, and barrier and electrical properties.
http://www.engineeringtalk.com/news/vic/vic159.html