Polyethylene heat pumps

Ground coupled heat pumps may now be feasible, largely due to the availability of durable and Inexpensive plastic pipe. Pipe materials such as polyethylene, FVC, and polybutylene have been found to be adequate In some Instances. However, no material standards or recommended design practices exist to facilitate the optimization of the performance, cost and reliability of these systems. 

The interface consists of (a) the nebulizer (b) the chamber (c) the membrane separator and (d) the torch. Organic solutions are fed to the nebuhzer via a peristaltic pump and the aerosol chamber is heated by a 2S0 W heating tape around the chamber. The membranes used are made from siHcone rubber and this is supported by high density polyethylene supports. A vacuum pump provides the vacuum on the membrane to remove the solvent vapour. 

The term QAP is the power required to pressurize the melt (pumping power) and represents less than 5% of the total power required for the process (9). Hence, as can be seen from Equation 3, the power requirement is essentially determined by the product CQAT. Typical processing temperatures are listed in Table III (10, 11. 12). Thus, it is found that high-density polyethylene requires the most power per pound of product while polystyrene requires the least. It should be noted that the average heat capacity values in Table II include the heat of fusion for the semicrystalline polymers such as high- and low-density polyethylene. 

In melt spinning, thermoplastic polymers (i.e. polymers which soften and melt when heated) such as polyamide or polyethylene terephthalate are made molten or liquefied in an extruder and are forced through the spinneret by a spinning pump. The filaments are then soUdilied by air-cooling. 

Two years elapsed before better and stronger equipment was available for further experimentation. When ethylene was heated to 180 °C in this new equipment, the pressure in the apparatus dropped unexpectedly, so more ethylene was pumped in. Then, when the reaction vessel was opened, the I.C.I. chemists found a large amount of white powdery solid, which was the long-sought polyethylene. Because they knew that the polymerization could not account for all of the pressure drop that had been observed, they suspected a leak in one of the joints of the apparatus. This idea led to the proposal that the polymerization had been catalyzed by oxygen in the air that had leaked into the apparatus, and this hypothesis was confirmed by experiments in which air was intentionally included with the ethylene. Oxygen can act as a radical initiator and catalyze the polymerization by a chain-reaction mechanism analogous to Equations 22.7-22.10. 

Fig. 10-19. Components used in the schematic manifold drawings. (a) Glass coils of x turns (2 mm i.d., coil diameter 17 mm, 180 per turn) (b) same as (a) but heated to r°C (25 °C stands for room temperature) (c) coil of x cm polyethylene tube, 0.5 mm i.d. and wild mounting if not specified otherwise (d) filter unit as specified in text (e) debubbler (f) flow cuvette, 2 mm i.d, x mm path length and y nm spectrophotometer wavelength and (g) pump tube on peristaltic pump with flow medium at x mL/min flow rate at standard pump speed.

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