Air cooled heat exchanger Texas City Texas

An inspection is, most generally, an organized examination or formal evaluation exercise. In engineering activities inspection involves the measurements, tests, and gauges applied to certain characteristics in regard to an object or activity. The results are usually compared to specified requirements and standards for determining whether the item or activity is in line with these targets, often with a Standard Inspection Procedure in place to ensure consistent checking. Inspections are usually non-destructive. Air cooled heat exchanger Texas City Texas

Inspections may be a visual inspection or involve sensing technologies such as ultrasonic testing, accomplished with a direct physical presence or remotely such as a remote visual inspection, and manually or automatically such as an automated optical inspection. Non-contact optical measurement and Photogrammetry have become common NDT methods for inspection of manufactured components and design optimisation. Air cooled heat exchanger Texas City Texas

A 2007 Scottish Government review of scrutiny of public services (the Crear Review, 2007 defined inspection of public services as “… periodic, targeted scrutiny of specific services, to check whether they are meeting national and local performance standards, legislative and professional requirements, and the needs of service users.” Air cooled heat exchanger Texas City Texas

A surprise inspection tends to have different results than an announced inspection. Leaders wanting to know how others in their organization perform can drop in without warning, to see directly what happens. If an inspection is made known in advance, it can give people a chance to cover up or to fix mistakes. This could lead to distorted and inaccurate findings. A surprise inspection, therefore, gives inspectors a better picture of the typical state of the inspected object or process than an announced inspection. It also enhances external confidence in the inspection process. See section 4.12 of the Crear report. Air cooled heat exchanger Texas City Texas

Due to the many variables involved, selecting optimal heat exchangers is challenging. Hand calculations are possible, but many iterations are typically needed. As such, heat exchangers are most often selected via computer programs, either by system designers, who are typically engineers or by equipment vendors. Air cooled heat exchanger Texas City Texas

To select an appropriate heat exchanger, the system designers (or equipment vendors) would first consider the design limitations for each heat exchanger type. Though cost is often the primary criterion, several other selection criteria are important:

High/ low-pressure limit Air cooled heat exchanger Texas City Texas

Air cooled heat exchanger Texas City Texas

Thermal performance Heat exchanger inspection Texas City Texas

Temperature ranges Air cooled heat exchanger Texas City Texas

Product mix (liquid/liquid, particulates or high-solids liquid) Heat exchanger inspection Texas City Texas

Pressure drops across the exchanger Heat exchanger inspection Texas City Texas

Fluid flow capacity Heat exchanger inspection Texas City Texas

Cleanability, maintenance and repair Heat exchanger inspection Texas City Texas

Materials required for construction Heat exchanger inspection Texas City TexasAbility and ease of future expansion Air cooled heat exchanger Texas City Texas

Material selection, such as copper, aluminum, carbon steel, stainless steel, nickel alloys, ceramic, polymer, and titanium. Heat exchanger inspection Texas City Texas

Small-diameter coil technologies are becoming more popular in modern air conditioning and refrigeration systems because they have better rates of heat transfer than a conventionally sized condenser and evaporator coils with round copper tubes and aluminum or copper fin that have been the standard in the HVAC industry. Small diameter coils can withstand the higher pressures required by the new generation of environmentally friendlier refrigerants. Two small diameter coil technologies are currently available for air conditioning and refrigeration products: copper microgroove and brazed aluminum microchannel. Air cooled heat exchanger Texas City Texas

Choosing the right heat exchanger (HX) requires some knowledge of the different heat exchanger types, as well as the environment where the unit must operate. Typically in the manufacturing industry, several different types of heat exchangers are used for just one processor system to derive the final product. For example, a kettle HX for pre-heating, a double pipe HX for the ‘carrier’ fluid and a plate and frame HX for final cooling. With sufficient knowledge of heat exchanger types and operating requirements, an appropriate selection can be made to optimise the process. Air cooled heat exchanger Texas City Texas

Monitoring and maintenance Heat exchanger inspection Texas City Texas

Air cooled heat exchanger Texas City Texas

Online monitoring of commercial heat exchangers is done by tracking the overall heat transfer coefficient. The overall heat transfer coefficient tends to decline over time due to fouling.

U=Q/AΔTlm Air cooled heat exchanger Texas City Texas

By periodically calculating the overall heat transfer coefficient from exchanger flow rates and temperatures, the owner of the heat exchanger can estimate when cleaning the heat exchanger is economically attractive. Heat exchanger inspection Texas City Texas

Integrity inspection of the plate and tubular heat exchanger can be tested in situ by the conductivity or helium gas methods. These methods confirm the integrity of the plates or tubes to prevent any cross-contamination and the condition of the gaskets. Air cooled heat exchanger Texas City Texas

Mechanical integrity monitoring of heat exchanger tubes may conducted through Nondestructive methods such as eddy current testing. Air cooled heat exchanger Texas City Texas

Fouling Heat exchanger inspection Texas City TexasMain article: Fouling Heat exchanger inspection Texas City Texas

A heat exchanger in a steam power station contaminated with macrofouling. Heat exchanger inspection Texas City Texas

Fouling occurs when impurities deposit on the heat exchange surface. Deposition of these impurities can decrease heat transfer effectiveness significantly over time and caused by:

Low wall shear stress Air cooled heat exchanger Texas City Texas

Low fluid velocities Air cooled heat exchanger Texas City Texas

High fluid velocities Air cooled heat exchanger Texas City Texas

Reaction product solid precipitation Heat exchanger inspection Texas City Texas

Precipitation of dissolved impurities due to elevated wall temperatures Heat exchanger inspection Texas City Texas

Air cooled heat exchanger Texas City Texas

The rate of heat exchanger fouling is determined by the rate of particle deposition less re-entrainment/suppression. This model was originally proposed in 1959 by Kern and Seaton. Air cooled heat exchanger Texas City Texas

Heat exchanger inspection Texas City TexasCrude Oil Exchanger Fouling. In commercial crude oil refining, crude oil is heated from 21 °C (70 °F) to 343 °C (649 °F) prior to entering the distillation column. A series of shell and tube heat exchangers typically exchange heat between crude oil and other oil streams to heat the crude to 260 °C (500 °F) prior to heating in a furnace. Fouling occurs on the crude side of these exchangers due to asphaltene insolubility. The nature of asphaltene solubility in crude oil was successfully modeled by Wiehe and Kennedy. The precipitation of insoluble asphaltenes in crude preheat trains has been successfully modeled as a first-order reaction by Ebert and Panchal who expanded on the work of Kern and Seaton. Air cooled heat exchanger Texas City Texas

Cooling Water Fouling. Localized precipitation of dissolved solids occurs at the heat exchange surface due to wall temperatures higher than bulk fluid temperature. Low fluid velocities (less than 3 ft/s) allow suspended solids to settle on the heat exchange surface. Cooling water is typically on the tube side of a shell and tube exchanger because it’s easy to clean. To prevent fouling, designers typically ensure that cooling water velocity is greater than 0.9 m/s and the bulk fluid temperature is maintained less than 60 °C (140 °F). Other approaches to control fouling control combine the “blind” application of biocides and anti-scale chemicals with periodic lab testing. Air cooled heat exchanger Texas City Texas

Maintenance Heat exchanger inspection Texas City Texas

Plate and frame heat exchangers can be disassembled and cleaned periodically. Tubular heat exchangers can be cleaned by such methods as acid cleaning, sandblasting, high-pressure water jet, bullet cleaning, or drill rods. Air cooled heat exchanger Texas City Texas

In large-scale cooling water systems for heat exchangers, water treatment such as purification, the addition of chemicals, and testing, is used to minimize fouling of the heat exchange equipment. Another water treatment is also used in steam systems for power plants, etc. to minimize fouling and corrosion of the heat exchange and other equipment. Heat exchanger inspection Texas City Texas

A variety of companies have started using waterborne oscillations technology to prevent biofouling. Without the use of chemicals, this type of technology has helped in providing a low-pressure drop in heat exchangers. Heat exchanger inspection Texas City Texas

In nature Heat exchanger inspection Texas City Texas

Air cooled heat exchanger Texas City Texas

Humans Heat exchanger inspection Texas City Texas

The human nasal passages serve as a heat exchanger, which warms air being inhaled and cools air being exhaled. Its effectiveness can be demonstrated by putting the hand in front of the face and exhaling, first through the nose and then through the mouth. Air exhaled through the nose is substantially cooler. This effect can be enhanced with clothing, by, for example, wearing a scarf over the face while breathing in cold weather. Air cooled heat exchanger Texas City Texas

In species that have external testes (such as humans), the artery to the testis is surrounded by a mesh of veins called the pampiniform plexus. This cools the blood heading to the testis while reheating the returning blood. Air cooled heat exchanger Texas City Texas

Birds, fish, marine mammals Air cooled heat exchanger Texas City Texas

Countercurrent exchange conservation circuit Heat exchanger inspection Texas City Texas

Further information: Countercurrent exchange in biological systems Heat exchanger inspection Texas City Texas

“Countercurrent” heat exchangers occur naturally in the circulation system of fish, whales and other marine mammals. Arteries to the skin carrying warm blood are intertwined with veins from the skin carrying cold blood, causing the warm arterial blood to exchange heat with the cold venous blood. This reduces the overall heat loss in cold waters. Heat exchangers are also present in the tongue of baleen whales as large volumes of water flow through their mouths. Wading birds use a similar system to limit heat losses from their body through their legs into the water. Air cooled heat exchanger Texas City Texas

Carotid rete Air cooled heat exchanger Texas City Texas

The carotid rete is a counter-current heat exchanging organ in some ungulates. The blood ascending the carotid arteries on its way to the brain flows via a network of vessels where heat is discharged to the veins of cooler blood descending from the nasal passages. The carotid rete allows Thomson’s gazelle to maintain its brain almost 3 °C (5.4 °F) cooler than the rest of the body, and therefore aids in tolerating bursts in metabolic heat production such as associated with outrunning cheetahs (during which the body temperature exceeds the maximum temperature at which the brain could function). Air cooled heat exchanger Texas City Texas