Pumps, heat plastic pipe

In the deep south of the United States, swimming pools are often solar heated. Plastic pipe collectors are in common use. Rows of black plastic pipes are laid on the south-facing roof of the house. The pipes are plumbed so that the pool pump can circulate some of the pool water through the pipes. The black pipes adsorb the solar heat and warm the water. In Florida a well-engineered system allows the use of pool a month or so earlier in the spring and a similar time later in the fall. Few solar systems are capable of heating the pool to a satisfactory temperature all year round. People who like to swim all year round use gas, oil or electric heat pump heaters in addition to their solar heaters. 

Plastic Pipe Requirements for Ground-Coupled Heat Pumps... 

This paper describes the temperature, pressure, fluid compatibility and mechanical strength requirements which must be met by plastic pipe materials for various ground coupled heat pump applications. Existing suitable materials are cited as well as areas where Improvements are required. 

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. 

Liquid source heat pumps typically require a fluid flow rate of roughly 5.4 x lO l/S per kW (3 GPM per ton) of heating capacity. In order to minimize circulation pump power, pipe (which ordinarily would be considered oversized for these flow rates) of 4 to 6 cm Inner diameter Is used. Earth coll lengths are typically 26 m per kW (300 ft per ton) of heating capacity. Thus, system operating pressures for a typical 11 kW (3 ton) heating load do not exceed 7-14 x 10 N/m (10-20 psl), lower than most existing schedules for plastic pipe. However, the system must also withstand water line pressure, l.e. 7 x 10 N/m (100 psl). 

Plastic pipe for ground coupled heat pumps must withstand Installation at depths of approximately 1-2 m for horizontal systems or In vertical shafts as deep as 100 m In vertical systems without extraordinary excavation precautions, as well as ground settling after Installation, and thermal stresses during operation without failure. 

Shortening and oil can also be handled in bulk. If the shortening is plastic, it is melted so that it can be pumped through pipes. These pipes must be heated throughout the plant to prevent the shortening from congealing. 

Following fires in which endotracheal tubes became ignited by surgical lasers or electrocautery in atmospheres enriched by oxygen and/or nitrous oxide, the flammability of PVC, silicone rubber and red rubber tubes in enriched atmospheres was studied [1], Ozonised oxygen was reacted with hydrogen at low pressure to generate hydroxyl radicals. Pressure in the apparatus was maintained by a vacuum pump protected from ozone by a tube of heated silver foil. On two occasions there was an explosion in the plastic vent pipe from the vacuum pump. The vent gas should have been outside explosive limits and the exact cause is not clear the editor suspects peroxide formation. 

Plastics production and utilization in terms of various forms such as pumps, billiard balls, valves, pipes, fans, nose cones, airplane canopies, hosiery, cabinets, pot handles, heat valves and other implants make one to realize the role played by them in everyday life. Plastics are produced by casting, molding, and extrusion and calendaring solid parts, lining, coatings, foams, fibers and films are also readily produced and available. 

Appendix A contains a materials selection guide for aerated freshwater systems. As indicated in Note 27 of Appendix A, in freshwater systems, admiralty brass should be limited to a maximum pH value of 7.2 from ammonia and copper-nickel alloys and should not be used in waters containing more sulfides than 0.007 mg/L The materials selection guide is also satisfactory for seawater, although pump cases and impellers should be a suitable duplex stainless steel or nickel-aluminum-bronze (properly heat treated). Neoprene-lined water boxes should be considered. For piping, fiber-reinforced plastic (up to 150 psi [1,035 kPa] operating pressure) and neoprene-lined steel should also be considered. Titanium and high-molybdenum SS tubes should be considered where low maintenance is required or the cost can be justified by life expectancy. 

The space between the two tanks is filled with layers of thin aluminized plastic film separated by a lightweight coarse plastic screen. These serve as a shield against the passage of thermal radiation from the outer to the inner tank. The air between the tanks and around the insulation is removed with a vacuum pump. The high vacuum serves to stop heat flow by conduction. The liquid fill and gas withdrawal lines are coaxial that is, one inside the other. They are made from materials with low thermal conductivity and are coiled inside the insulation to minimize heat flow down the length of the pipe from the outside into the inner tank. 

Extrusion is a continuous process in which an Archimedes screw, rotating within a heated barrel, melts and pumps the polymer through dies to form continuous shapes such as pipes, profiles or sheets. In addition, extrusion is the basic element in a number of other polymer processing operations. The plastication and pumping functions... 

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