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.
Classification
Heat exchangers are classified according to their flow arrangement. In parallel-flow heat exchangers, the two fluids enter the exchanger at the same end, and travel in parallel to one another to the other side. In counter-flow heat exchangers the fluids enter the exchanger from opposite ends. The counter current design is most efficient, in that it can transfer the most heat from the transfer medium. In a cross-flow heat exchanger, the fluids travel perpendicular to one another through the exchanger.
For efficiency, heat exchangers are designed to maximise the surface area of the wall between the two fluids, while minimising resistance to fluid flow through the exchanger. The exchanger’s performance can also be affected by the addition of fins or corrugations in one or both directions, which increase surface area and may channel fluid flow or induce turbulence.
The petrochemical industry has specifications for manufacturing, which heat exchangers must meet. ASME (American Society of Mechanical Engineers), TEMA (Tubular Exchangers Manufacturers Association) and API (American Petroleum Institute) codes and specifications are the most commonly used. “Nowadays, the European standard PED (Pressure Equipment Directive) is also finding wider acceptability,” says Perumal Sukumar, senior sales manager at Dolphin Radiators and Cooling Systems.
Shell & Tube
The most basic and the most common type of heat exchanger construction is the tube and shell, it consists of a set of tubes in a container called a shell. The fluid flowing inside the tubes is called the tube side fluid and the fluid flowing on the outside of the tubes is the shell side fluid. At the end of the tubes, the tube side fluid is separated from the shell side fluid by the tube sheet(s).
The tubes are rolled and press-fitted or welded into the tube sheet to provide a leak tight seal. On systems where the two fluids are at vastly different pressures, the higher pressure fluid is typically directed through the tubes and the lower pressure fluid is circulated on the shell side.
“Shell and tube as well as plate type heat exchangers find applications in the petrochemical industry. However, shell and tubes have more application due to their versatility and higher pressure capability. Plate heat exchangers are however more compact and useful below pressures of 25 bar”, says Sukumar.
This is due to economy, because the heat exchanger tubes can be made to withstand higher pressures than the shell of the heat exchanger for a much lower cost. The support plates also act as baffles to direct the flow of fluid within the shell back and forth across the tubes.
Plate exchange
A plate heat exchanger uses metal plates to transfer heat between two fluids. This has a major advantage over a conventional heat exchanger in that the fluids are exposed to a much larger surface area, because the fluids spread out over the plates. This facilitates the transfer of heat, and greatly increases the speed of the temperature change. It is not as common to see plate exchangers because they need well-sealed gaskets to prevent the fluids from escaping, although modern processes have made them feasible.
“Plate and frame heat exchangers are suitable for offshore platforms too, as it saves money and space” says Uttam Vishwasrao, service manager at Tranter
Heat Exchanger.
A regenerative heat exchanger (regenerator), is a type of heat exchanger where the flow is cyclical and periodically changes direction. It is similar to a countercurrent heat exchangers. However, a regenerator mixes the two fluid flows while a countercurrent exchanger maintains them separated. The temperature profile remains at a nearly constant temperature, and this includes the fluid entering and exiting each end.
In order to select an appropriate heat exchanger, system designers consider the limitations for each product by type. Although cost is often the first criterion evaluated, there are several other important selection factors which incorporate thermal performance, high/low pressure limits, temperature ranges, product mix, and fluid flow capacity.
Business booming
A recent report published by Global Industry Analysts estimates the heat exchangers market will exceed US$12.7 billion by 2012. Europe represents the largest heat exchangers market, and is estimated to account for a share of over 36% in 2008. Asia-Pacific represents the fastest growing heat exchangers market, exhibiting a compounded annual growth rate of 4.8%.
“The demand from the petrochemical sector is good at the moment. However, we expect a slow down in the second half of this year in line with the reduction of oil prices, which has caused several projects to be put on hold” says Sukumar.
“The sector expanded rapidly recently due to the large number of new projects in the Middle East. However, some slow down is expected due to the rapid fall in the oil prices,” he added.
“While the industry is slowing down, we expect things to look up from 2010 onwards” says Sukumar.
“The current market situation is not encouraging, as it obliged many company to freeze their orders, for instance, the Saudi mega petrochemical company of PetroRabigh has put on hold a request to buy plate heat exchanger” says Rahul Patil, sales manager at GEA Group Company.
Sales of heat exchangers to the chemical industry, the largest end-use segment, are projected to reach $2.7 billion by 2012. Heat exchanger sales to the fuel processing industry, the fastest growing end-use segment, are projected to expand at a CAGR of 3.2% over the period 2000-2010. Deriving growth from the astronomical prices of oil in the world, investments in fuel processing industry are expected to increase in the near future.
Shell and tube heat exchangers market, the largest product segment, is projected to exceed $3.5 billion by 2015.
Europe, the largest market within the segment, is projected to grow at a compound annual growth rate of 2% over the period 2000-2010.
Productivity improvements, in terms of enhanced efficiency, greater durability, and lowered fouling, are set to revitalise the shell and tube market.
Plate and frame heat exchangers market, the fastest growing segment, is projected to register a CAGR of 4.8% over the period 2000-2010. Asia-Pacific is the fastest growing market in plate and frame heat exchangers, and is projected to grow at a CAR of 7.5% during the period 2000-2010.
Shell and tube exchangers are forecast to retain their market dominance over the analyzed period, while plate and frame exchangers, air coolers, and other heat exchangers are slated to witness rapid market expansion. Chemicals and refrigeration industries are expected be the major end-users.
European shell and tube exchangers market is undergoing a phase of cutthroat competition, which is adversely affecting the margin of domestic companies. While low cost heat exchange suppliers such as from Italy are continuing to storm the North European regions (UK and Germany), those from outside of Europe have also been fueling the aggressive price war. Foreign entrants include suppliers from South Korea, China, and India.
This has led to manufacturers shifting production base to low cost East European regions, in order to sustain their margins and remain competitive. High metal prices and energy costs have had a direct impact on the profitability of heat exchanger manufacturers in the region. Although companies are devising strategies to sustain their markets, pricing pressure is expected to continue in the coming years.
