Showing posts with label tube bundle. Show all posts
Showing posts with label tube bundle. Show all posts

Thursday, November 17, 2016

Shell and Tube Heat Exchanger Refurbishment

shell and tube heat exchangers tube bundle removed for refurbish
Two shell and tube heat exchangers getting refurbished
at industrial site. Tube bundles have been removed.
Shell and tube heat exchangers are regularly employed throughout industrial and commercial sites as a means of producing heated or cooled fluids. They consist of a pressure vessel and an internal tube bundle. The flow paths of the pressure vessel and the tube bundle are isolated from one another, giving a shell and tube heat exchanger four nominal connections.

  • Vessel inlet
  • Vessel outlet
  • Tube bundle inlet
  • Tube bundle outlet
Most often, the subject process fluid to be heated or cooled will flow through the pressure vessel, contacting the surface of the tube bundle contained within. If the heat transfer fluid flowing through the tubes is warmer than the process fluid in the vessel, heat will conduct through the tube wall into the process fluid, increasing its temperature. If the fluid in the tube bundle is cooler than the process fluid in the vessel, the process operates in the reverse fashion. Construction details of shell and tube heat exchangers can vary, but the basic operating scheme remains constant.

The lack of moving parts and ruggedly constructed nature of shell and tube heat exchangers tends to grant them a good measure of longevity for most applications. Regardless of any exceptions to that statement, there will eventually come a time when refurbishment or replacement is needed. If the pressure vessel is serviceable, or can be made so with a reasonable amount of cost, replacing the tube bundle may be the main element of an operation aimed at returning the heat exchanger to like new service.

Tube bundles are just that, bundles of tubes. With the right set of dimensional information and specifications, an identical fabrication can be purchased and put in place. It is not always necessary to revisit the original manufacturer. If drawings are still on file for the unit, sufficient information can be gleaned from them to produce a replacement tube bundle that will provide rated performance.

Ordering up a replacement tube bundle is not complicated, but the operation can be smoothed out through contact with involvement of an experienced engineer that can make sure all the necessary information is on hand and step you through the process. 

Tuesday, September 20, 2016

Replacing Heat Exchanger Tube Bundles

heat exchangers outdoors at oil refinery
Heat exchangers of many sizes are used throughout industry
Heat, a well recognized energy component of countless industrial processes. Heat exchangers are employed to move or transfer heat between two media, and are available in a wide variety of designs and configurations. They are manufactured from materials and in forms to accommodate the specific performance requirements of each process, machine, or operation.

The shell and tube heat exchanger is one common type of this heat transfer device that can be found in many commercial buildings and industrial plants. The unit is comprised of a vessel, or shell, with an array of tubes contained within. One fluid will flood the shell, encompassing the tubes through which a second fluid passes. The contact between the fluid within the shell and the outer surface of the tubes facilitates the transfer of heat energy between the two media. Applications for shell and tube units typically involve two liquids or one liquid and steam. They are not suitable for applications involving air streams.

Eventually, all heat exchangers need either major overhaul or replacement. Tubes tend to deteriorate faster than the shell, so replacement of the tube bundle can breathe extra life into a heat exchanger. Original documentation provided with the unit, plus a physical inspection, should provide all the information needed to have a new tube bundle manufactured. Numerous sources are available for replacement tube bundles, with the original manufacturer being only one potential source.
The replacing of a heat exchanger is also a good time to examine the performance delivered by the existing unit. Was it a limiting factor in the operation of the process? If so, perhaps this may be an opportunity to build in some headroom. Whatever the case, recognize that bringing in a product specialist with experience and knowledge will provide the beneficial leverage you need to get the job done right and finished on time.

Tuesday, December 30, 2014

Heat Exchangers for Liquid-Gas Vaporization

Tube bundle for heating
Tube bundle for heat transfer.
Hydrocarbon and non-hydrocarbon based gases can be more efficiently stored and transported in a liquified state, providing higher media density and corresponding product weight per container. Upon reaching their final destination, the liquid can be reheated, returning to a gaseous state for distribution and use. Typical liquified gases include natural gas, oxygen, butane, propane, and nitrogen.

There are several ways to affect the physical change from liquid to gas, and picking the best option is dependent on criteria such as; 1) available energy sources; 2) plant location; 3) climate conditions; and 4) plant infrastructure.

The change from liquid to gas phase usually requires one or more vessels properly sized and designed to accommodate the vastly increased volume of the evaported liquid, handle the storage or distribution pressure of the gas, and be compatible with the process media. In most plants today, the gradual process of warming the liquified gases is done with steam-heated or oil-heated "heat exchangers" or "tube bundles".

Some heat exchanger systems may, instead of steam, use steam-heated intermediary fluids such as oil, water, or glycol-water solution to provide a smoother rate of heat transfer to the evaporating liquid. This method can employ two heat exchangers, one transferring heat from steam to the intermediary fluid, then another to transfer heat from the intermediary fluid to the liquified gaseous product to evaporate it.

Steam heated, closed-loop circulation systems play an important role in providing an efficient, low-cost and compact method to accommodate liquid vaporization. Steam is available in many industrial plants, providing a comparatively inexpensive and readily available source of heat energy. Heat exchangers are available in a range of pre-engineered capacities and forms, but it is quite common for these components to be custom fabricated to meet very specific requirements. Engineers can design their own systems from the component level, or provide performance requirements to the manufacturer and have a skid mounted unit produced, ready for connection to electric power (for control systems), energy source (steam, oil or water) and process inlet and outlet lines.

These systems can be quite technical, with numerous design considerations. The path to maximized safety and efficiency includes consultation with a heat exchanger expert as part of specification and design process. A combination of your high level process knowledge and their product and application expertise will yield the best outcome.

Thursday, October 23, 2014

Basics of Heat Transfer


basic heat transfer
Heat moves from hot to cold
(image courtesy of ces.fau.edu)
In nature, the laws of physics will continually drive energy in an attempt to reach equilibrium. In a thermal loop, as long as there is a temperature difference, heat moves away from the warmer entity to the cooler entity.

Heat exchangers facilitate this phenomena with tube bundles and vessels which separates the hot medium from the cold. Heat penetrates the surface of the tubes and is transferred to the contents of the vessel, thereby heating or cooling fluids or gases in the vessel or in the tubes.

Wednesday, September 17, 2014

Shell and Tube Heat Exchangers for Industrial and Commercial Application

tubing bundle
Tube Bundle
A shell and tube heat exchanger is a type of heat exchanger consisting of a shell (a pressure vessel) with a tubing bundle (or core) inside. Two fluids are used, one inside the tubing and one outside the tubing, to change temperature of the fluid contained in the shell. The amount of surface area provided by the tubes determines the efficiency of the heat transfer, and is sometimes augmented by additional lengths of tubing, or with fins.

The function of a shell and tube heat exchanger is very basic. Two different fluids, physically isolated from each other, and at different temperatures, are allowed to transfer thermal energy from one to the other through thermal conductivity.