Far infrared fiber can emit a low dosage of far infrared ray and provide heat retention and thermal energy properties; it can be used as health textiles that make it possible to meet people's requirement of far infrared therapy, improve the microcirculation of the body, and promote metabolism. Ceramic powders are always used into the far infrared fibers, as listed in Table 2.36.
Table 2.36. Chemical composition and physical properties of the far infrared ceramic powder used in fibers
Empty Cell
Chemical formula
Color
Grain size (μm)
Density (g/cm3)
Ultrafine titanium dioxide
TiO2
White
0.02–0.10
4.0
Ultrafine zinc oxide
ZnO
White
0.01–0.04
5.5–5.8
Zirconium carbide
ZrC
Grey and black
1.2–2.0
3.2–3.3
Aluminum oxide
Al2O3
White
0.6–1.0
3.9–4.0
Zirconium oxide
ZrO2
White
0.02–0.10
3.3–3.5
Stannic oxide
SnO2
White
0.01–0.06
6.9
Magnesium oxide
MgO
White
0.3–1.0
3.0
Sun J, Lv W. New fiber material. Shanghai: Shanghai University Press; 2007. p. 361.
For example, Solar-Aloha, developed by Descente and Unitika in Japan, can absorb light of less than 2-μm wavelength, and it converts it to heat owing to its zirconium carbide content. In winter, the fiber can use the cold winter sun to capture more than 90% of this incident energy to keep the wearer warm.
Passive systems are explored as a means to abate two major environmental problems plaguing metropolitan areas – poor air quality and heat retention. As the sources of these problems are diffuse, the solutions must also be diffuse and dispatched throughout the urban framework. A passive system is one that can be incorporated into an existing infrastructure and can function only utilizing primary energy sources. Two types of passive systems are discussed in this chapter – photocatalytic building materials, which utilize sunlight to drive the chemical conversion of air pollutants, and vegetative cover, which is a sink for air pollutants and a source of passive cooling.
DALE BUCHBINDER, SHARON B. BUCHBINDER, in Venous Ulcers, 2007
XENOGRAFTS
Xenografts serve as biologic dressings and protect wounds from bacterial and physical trauma, reduce pain, and increase moisture and heat retention.19 While not a replacement for human skin, xenografts do serve as a barrier until the wound is able to heal. They go back as far as the 16th century and have been obtained from species as varied as dogs, cats, rats, chickens, bullfrogs, sheep, cows, and pigs. Porcine xenografts are used most commonly because they are cheap and readily available. The wound should be debrided and, if infected, antibiotics should be initiated. The porcine skin is more likely to adhere if the wound is clean than if it is infected. Porcine xenografts can be used in conjunction with meshed allografts; however, they need to be inspected and changed weekly before rejection occurs. Compression therapy should be applied to reduce edema, and the patient should be seen at least once a week, at a minimum, to assess wound healing.
The mid insulation layer may be varied in thickness, or bulk, in its ability to trap ‘still air’ for heat retention. It may constitute more than one garment with examples such as jackets, smocks, gilets, traditional knitwear, and felted garments. Typically, the insulation is made up of lightweight man-made down, sliver knit constructions, known as fibre pile or fake fur, and increasingly sophisticated developments in knit structure fleece fabrics, primarily in weft knit, and predominantly of polyester fibre. Fleece pile garments may have ‘body mapped’ engineered knit in varying patterning, depths of pile and finishes to provide variable protection around the body (McCann, 2013; McCann et al., 2009). Older people are susceptible to cold and may benefit from adaptations of existing and emerging technologies initially adopted in performance sportswear, such as heated panels (Fibretronic.com). Mid layer garment design should be compatible, in terms of cut and styling, with that of the base and outer layer garments, to avoid impeding movement and friction between the layers.
Pipeline burial adds cost to the installation process because of the need for route selection and extra equipment to perform burial operations. In deepwater, operators may bury pipe to increase heat retention for flow assurance, and in shallow water may be required by regulation to bury pipe. In the U.S. Gulf of Mexico, pipelines greater than 8 and 5/8 inches and installed in water depths less than 200 feet are required to be buried at least three feet below the mudline. Burial cost may account for a significant portion of the total installation cost. For example, in the Mars export line in the Gulf of Mexico, burial costs were $16/ft relative to a lay cost of $56/ft. In the Garden Banks line, burial costs were about half of the lay cost, and in the Nautilus pipeline, burial costs were $10/ft relative to lay costs of $35/ft (Kaiser, 2017).
Heat losses of the storage vessel to the surroundings can severely diminish the heat storage efficiency. The overall heat loss coefficient of a storage system and the surface area of the storage tank are the major factors that decide the heat retention capacity of the storage system. The overall heat loss coefficient of a storage system is evaluated by conducting an experiment as detailed herein.
The storage medium in the tank is raised to a higher operating temperature (T1) and left undisturbed. The temperature in the storage tank decreases slowly, and the average temperature inside of the storage tank is recorded at a regular interval of time and the variation of temperature with respect to time is observed. The experiment should be continued until the storage tank reaches the lower operating temperature (T2) of the storage system. The overall heat loss coefficient is evaluated using Eq. [15.5]:
[15.5]
where UL is the overall heat loss coefficient (W/m K), m is the mass of the storage medium (kg), cp is the specific heat capacity of the storage medium (J/kg K), T1 is the temperature of the storage medium at the initial time (K), T2 is the temperature of the storage medium at the end of the experiment (K), T∞ is the average ambient temperature during the conduct of experiment (K), t is the time taken for the temperature to reach T2 from T1 (s), As is the surface area of the storage tank (m2), and LMTD is the log mean temperature difference (K).
The heat loss from the storage tank in a given interval of time (Δt) is evaluated using Eq. [15.6]:
The atmosphere surrounding earth is composed of layers of gases, or called air, that are retained to surround earth by the latter’s gravity. The atmosphere absorbs ultraviolet solar radiation, warms the surface of earth through heat retention (which is the so-called ‘greenhouse effect’) and reduces temperature extremes between day and night. As a result, the atmosphere of earth provides a natural protection of life on earth.
Specifically, dry air contains about 78.08% nitrogen, about 20.95% oxygen, about 0.93% argon and small amounts of other gases. Air also contains a variable amount (0–5%) of water vapor, which is much higher at sea level than in the rest of the entire atmosphere (Wallace & Hobbs, 2006, p. 8). Air content and atmospheric pressure vary at different layers. There are five basic layers of the atmosphere surrounding earth: troposphere, stratosphere, mesosphere, exosphere and thermosphere (Fig. 7.1) (Source: http://www.srh.noaa.gov/srh/jetstream/atmos/layers.html Accessed 30.11.16. In what follows in this subsection, unless stated otherwise, all definitions relating to the data on the five atmospheric layers are based on this website).
Meteorologically, the troposphere begins at the surface of earth and extends from 6 to 20 km in height. Known as the lower atmosphere, the troposphere encompasses almost all weather phenomena. The height of the troposphere varies: It is around 18–20 km high at the equator, but is only less than 2.5 km high at the poles. As the density of the gases decreases with respect to height, the air becomes thinner accordingly. Therefore, the temperature in the troposphere also decreases with respect to height. As one climbs higher, the temperature drops from an average of about 17°C (or 62°F) to that of about −51°C (or −60°F) at the tropopause.
This part of the atmosphere is the densest. Almost all weather is in this region.
The stratosphere extends around 50 km down to anywhere from around 6–20 km above earth’s surface. This layer only contains about 19% of the atmosphere’s total gases, with little water vapor. In this layer the average temperature increases with height. Heat is produced in the process in which the ozone is formed (Box 7.1). This heat is responsible for temperature increases from an average of about −51°C (or −60°F) at the bottom of the stratosphere to a maximum of about −15°C (or 5°F) at the top of the stratosphere.
Box 7.1
How the Ozone Depletion Matters
Ozone depletion describes two distinct but related phenomena observed since the late 1970s: (1) a steady decline in the total amount of ozone in earth’s stratosphere (i.e., the ozone layer), and (2) a much larger springtime decrease in stratospheric ozone around earth’s polar regions. The latter phenomenon is referred to as the ozone hole. The details of ozone-hole formation in the polar differ from those of mid-latitude thinning, but the most important process of both of which is catalytic destruction of ozone by atomic halogens. The main source of these halogen atoms in the stratosphere is photodissociation of man-made halocarbon refrigerants, solvents, propellants and foam-blowing agents (including chlorofluorocarbons (CFCs) and others). These compounds are transported into the stratosphere by winds after being emitted at the surface. Both types of ozone depletion increase as the emissions of halocarbons increase.
CFCs and other contributory substances are referred to as ozone-depleting substances. Since the ozone layer prevents most harmful wavelengths of ultraviolet (UV) light – an electromagnetic radiation with a wavelength from 10 nm (30 PHz) to 400 nm 750 (THz) – from passing through earth’s atmosphere, the decrease in ozone generated worldwide concern, leading to adoption of the Montreal Protocol that bans the production of CFCs and other ozone-depleting chemicals. It is suspected that a variety of biological consequences such as increases in sunburn, skin cancer, cataracts, damage to plants and reduction of plankton populations in the ocean’s photic zone may result from the increased UV exposure due to ozone depletion.
The mesosphere layer starts just above the stratosphere and extends from about 50 km above earth’s surface to about 85 km. The density of gases which mainly include the oxygen molecules decreases as one descends. As a result, the average level of temperatures increases as one descends, which rises to about −15°C (or 5 °F) near the bottom of this layer. The gases in the mesosphere, though not as thick as those in the stratosphere, are still thick enough to slow down meteors hurtling into the atmosphere. Meteors are eventually burnt up in the atmosphere, leaving fiery trails in the night sky. Both the stratosphere and the mesosphere are considered the middle atmosphere. The transitional boundary which separates the mesosphere from the stratosphere is called the stratopause.
Between about 85 and 600 km lies the thermosphere. This layer is also called the upper atmosphere. Aurora and satellites are usually found to occur in this layer. While still extremely thin, the density of gases of the thermosphere continues to decrease as the height rises. Nevertheless, the incoming high-energy ultraviolet and X-ray radiation from sun can still be absorbed by the molecules in this layer, thus causing a large increase of temperatures. In the thermosphere, the temperature increases with height. From as low as about −120°C (or −184°F) at the bottom of this layer, the average temperature can reach as high as about 2000°C (or 3600°F) near its top.
The exosphere is the outermost layer of the atmosphere. It starts at the top of the thermosphere and extends to around 10,000 km above the earth. In this layer, gases are far thinner than those in the thermosphere, while the density of gases continues to decrease as the height rises.
Comfort describes “how materials interact with the body and addresses how the body's functional environment can be expanded” (Kadolph, 2007, p. 187). Comfort is studied by looking at fabric in terms of elongation and elasticity, heat retention and conduction, moisture absorbency, water repellency, waterproofing, hand and skin contact, drape, and air permeability (Nayak et al., 2009). Elongation is the fabric's ability to stretch without recovery, whereas elasticity is the fabric's ability to stretch and recover to its original dimension without distortion. Heat retention and conduction of a fabric addresses the way the body reacts to heat. Moisture absorbency is the ability of a fabric to absorb liquid water. Water repellency is a fabric's ability to repel water or other liquids upon initial wetting. This is usually accomplished with a combination of densely woven material and a water-repellent finish. Water will soak through the fabric with extended time and pressure of water. Waterproofing, on the other hand, is a fabric that will not allow water to penetrate through it no matter how much exposure to water, duration, and pressure used. Water repellent and waterproof fabrics are often seen as uncomfortable due to their stiffness and inability to breathe. Hand and skin contact is the way a fabric feels to the touch. Drape is how well a fabric hangs over a body or object. Fabrics with more drapes bend easily around objects and are often seen as more comfortable because the fabric moves with the body. Fabrics with less drape are stiffer and hang away from the body.
This is the last item to be considered, but arguably the most important. The purpose of curing is discussed in Chapter 20.
Some methods of curing are:
•
Wrap elements (e.g., columns) in polythene after removing shutters.
•
Spray with curing membrane after removing shutters.
•
Cover slabs with polythene (and pour ground slabs on polythene).
•
For heat retention, use polystyrene on the back of shutters (especially, steel ones).
•
Simply leaving shutters in place for a few extra days (especially wooden ones).
•
50 mm of sand can work on slabs.
•
Ponding (i.e., forming a pool on the concrete surface) is by far the most effective.
Note about curing:
•
Curing is not usually priced as a separate item – this does not mean that no money may be spent on it.
•
Make sure that curing is applied as soon as possible. A few hours may make a substantial difference.
•
Spray-on curing membranes are not very effective, and in windy conditions they are often useless. On difficult areas (such as columns) they may, however, be the only option.
•
Remember that PFA, GGBS and, especially, CSF need much better curing (often 5 days, rather than 3 days).
•
Permitting the bleed water to dry off will encourage more bleeding, and plastic cracking.
•
Slabs on ground should have a polythene sheet placed under them, to prevent excessive water absorption by dry soils.
Pipelines greater than 8 and 5/8 in diameter and installed in water depths less than 200 ft in the Gulf of Mexico are required to be buried at least 3 ft below the mudline. In deepwater, operators may bury pipe to increase heat retention for flow assurance. Burial costs normally account for a significant portion of the installation cost. For example, in the Mars export pipe line, burial costs were estimated to be $16 per foot relative to a lay cost of $56 per foot. For the Garden Banks pipe line, burial costs were estimated to be about half of the lay cost, and in the Nautilus pipeline, burial costs were $10 per foot relative to lay costs of $35 per foot.