Hot air blowers

A amimon heating method in industry is using blowers that blow heated air into the room. See Fig. 8.57, An advantage is that the installation costs are low. A possible disadvantage is that it mixes the air in the room, which may not be desirable in combination with displacement ventilation. 

When locating hot air blowers, we need to know the penetration depth for the hot air that is being discharged from the blowers. For a given discharge angle the penetration depth, z, can he expressed as 

AT - temperature difference between the discharged warm air and the room air (K) 

FIGURE a.sa Penetration depth versus Archimedes number and discharge angle. 

A room is heated by hot air blowers. The indoor temperature is +10 °C. Each blower has the following data  

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This means that the hot air blower should not be placed more than 4,2 in above the floor. 

An oven in the form of a tunnel mounted over or containing a continuous conveyor belt is used to shrink oriented films in the shrink packaging process. Also use a hot air blower on the film to provide the heat required in specific areas. 

A PTFE tube (1), for example, with an outer diameter of 3 mm and an inner diameter of 2 mm, is cut some centimeters longer than finally needed. Tubes from 0.5 mm up to 6 mm outer diameter have been successfully applied with this method. The tube is heated at the end (ca. 2-3 cm) with a hot air blower until it becomes clearly transparent (2, ca. 250 °C, using a gas flame includes the risk of overheating and decomposition of the polymer). Then the tube is quickly stretched so that the diameter becomes smaller than the borehole (3). The squeezed end is cut off (4). 

The tube is now immersed nearly up to its neck in an oil or metal bath and the -amino-caproic acid melted at a bath temperature of220 °C.Then it is heated quickly to 260 °C and held at this temperature under a continuous stream of nitrogen for 15 min. Should any water condense on the wall of the connecting tube leading to the calcium chloride tube, it can be removed by warming with a hot-air blower before the heating bath is taken away and the melt allowed to cool under nitrogen. Finally, the tube is broken and... 

Further physico-chemical considerations which must never be forgotten are that, as implied above, heat must be steadily removed from the receiving vessel by some form of cooling and heat must be supplied to the source of the distillate. The heating rarely presents a problem, as water baths or hot air blowers are suitable for small vessels, say up to 0.5 1, and heating mantles or tapes for larger vessels. 

The reagent is a potent skin irritant and may cause sensitisation it must be handled with care. Material of good quality (c. 99% pure) is available commercially as a waxy low-melting solid, m.p. 34-35 °C. It is most convenient to liquefy the reagent by the use of a hot-air blower or by standing the reagent bottle in a little warm water to assist weighing out. 

The filter cell, the reaction cell, and the windows of the bath were all of fused quartz. The lens, bath, and photomultiplier tube housing were rigidly mounted on an optical bench. Temperature control inside the bath was achieved by using either a circulating water pump ( 0.25°C.) or a hot air blower (=fcl°C.). 

Method. Apply 25 p, of the reference solution to the first column of the plate, and apply 25 ]al of the acidic extract from the solvent extraction mediod, or of the column extract, to the next column on the plate. Use a lOO-p, gas-chromatography syringe for Ihe application, taking great care to wash the syringe several times with chloroform between the application of each extract. Develop the plate in a tank containing chloroform acetone (4 1) (System TD, p. 168). After development, remove the plate and dry under a hot-air blower. 

The extract is examined using silica gel G plates and ethyl acetate as the mobile phase (System TF, p. 168). Score the plates vertically to bring about an even movement of the mobile phase, and score a horizontal line 10 cm from the bottom of die plate to mark the distance travelled by the solvent front Dissolve the residue from the extract in 100 jiil of acetone and immediately apply 30 )li1 to die plate at the same time apply lO-pl portions of each reference solution. After development, dry the plate with a hot-air blower. 

Remove the plates and dry under a hot-air blower. Location Reagents. Danthron is visible as a yellow spot on the first plate, or as an orange spot on the second plate. Examine the plates under ultraviolet light at 254 nm and 366 nm. All the substances absorb at 254 nm danthron and rhein give an orMige fluoresence at 366 nm. 

A line is drawn witii a pencil p allel to, and 2 cm from, the bottom of the plate. The s ples e spotted on to this line, called the origin, starting 2 cm from die side of the plate and at least 1 cm fi-om each odier. The sample, normally 1 to 10 pg of material depending on the thickness of the plate, is applied in as small a volume of solvent as possible (usually 1 to 10 jU). It may be applied by a micropipette (commercially available products deliver a known volume with an accuracy of 2%), by a capillary tube drawn out to a fine point, or by a calibrated micro-syringe. Whichever way it is applied, it is vital diat the spot is no more thm 4 mm in diameter or resolution will be lost. The plate surface must not be cut or gouged by the applicator. The solvent used to apply the spot should be volatile and have low polarity so that the spot does not difruse too much. The solvent may be applied to the plate in aliquots, and dried off naturally or by use of a hot air blower. It is essential that the spot is dry at the end of application, especially if the solution contains water. Even a small amoimt of a polar solvent adsorbed on the plate can drastically alter chromatographic properties. 

Once the plate has been developed for the predetermined distance, it is removed from tiie tsmk and the position of the solvent front quickly marked before any solvent evaporates. The solvent can tiien be allowed to evaporate naturally or removed with a hot air blower. 

Grubb et al. have used a hot air blower shown in Fig. 39. It took 13 s to get within 1 °C of the temperature of the hot air (128 °C). This design cannot be used for air sensitive polymers although one could possibly use inert gas instead of air. 

Thermal Analysis. A new or reassembled sample tube received the following conditioning treatment. It was evacuated, filled with gaseous fluorine to a pressure of about 1 atm., and periodically heated with a hot-air blower. After 1-15 hours, the fluorine was removed, and the tube was evacuated and weighed to obtain a tare. 

It is recommended that a water or oil bath, or a hot air blower, be used for this distillation to avoid the risk of local overheating. 

A method of detecting many substances with iodine vapor is nonspecific but usually does not cause decomposition. It is therefore recommended for laboratories in which TLC is often used and where old or slightly damaged 20 x 20 cm flat-bottomed chambers are always kept ready for use for this type of vapor treatment. These contain two small porcelain dishes containing elementary iodine. After introducing one or two 20 x 20 cm TLC plates or more plates of smaller format up to 10 X10 cm, hot-air blowers are used to heat the outer wall of the chamber until violet vapors appear. 

After complete removal of the ammonia (ca. 30 min heating by a hot air blower), the plate is sprayed with solution A and then heated at 160 °C for 10 min. After cooling the plate to room temperature, it is then sprayed with solution B. 

In the distillation of substances of low volatility at atmospheric and reduced pressures a short column is all that is employed and its function is mainly to act as spray trap. Coarse packing, placed on a gauze support, is used plate columns are unsuited for such purposes. It is obvious that the column should be provided with a heating jacket and that no part of the apparatus, from the stiU pot to the condenser, should be unheated, so that there may be no partial condensation. The receivers should also be capable of being warmed. A useful measure is to heat the take-off valve by radiation from an infrared source or by a hot air blower (hair dryer), so as to prevent it from sticking. Better still is the use of magnetic valves. 

Column heating is usually carried out either by steaming (Sec. 11.8), by circulating liquid (Sec. 11.10), or by hot air blowers. In freezing climates, hot air blowers are often used to warm up the column prior to steaming or liquid circulation. 

The reactor is now cooled with liquid nitrogen and the entire system evacuated to about 0.1 mm. The cold bath is removed and the second flask (at the manifold) is cooled within a few minutes, CI3 and CIO3 distill with foaming. To remove these gases completely, the vessel is immersed in a bath at + 20°C for one half hour and vacuum is applied. As soon as no further volatiles distill, the bath temperature is raised to about 35-36°C. The Cr03(Cl04)3 now distills into the manifold and flows into the first ampoule (transparent red liquid). The manifold with the ampoules should be somewhat inclined. When sufficient compound has collected in the first ampoule, the latter is sealed off. Additional distilled product collects in the stub left from the first ampoule, and is driven into the next ampoule by heating with a hot-air blower. 

Hi) The final drying is afforded by the help of Hot-Air-Blower (supplied by Gallen-kamp). 

Hot-Air-Blower. A sturdy, heavy duty power-driven blower that functions on a simple principle i.e., it draws air through a filter, passes it through a heater, and forces it upwards through pointing tubes that hold the apparatus. 

Jeweller s forceps and dissecting scissors FST Inc., 202-277 Mountain Highway, North Vancouver, BC V7J 3P2, Canada. Fax. (604) 987-3299. Electrical wire, conducting paint, hot air blowers and other sundnes RS Components Ltd., P.O. Box 99 Corby, Northants NN17 9RS, UK. Fax +44 (0)1536 405678... 

Either use a hot air blower (for paint stripping), or put the cup on a layer of aluminium foil in an oven at 120 °C and note the gradual shape reversion to a nearly-flat sheet (Fig. 1.16b). The thermoforming process involved the elastic stretching of a sheet of polymer melt, and this orientation was frozen into the cup when it cooled. On reheating, the plastic attempts to return to its original shape. 

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