Cold water pipes

OTEC power plants can be located either onshore or at sea. The electricity generated can be transmitted to shore by electrical cables, or used on site for the manufacture of electricity-intensive products or fuels (such as hydrogen). For OTEC plants situated on shore to be economical, the floor of the ocean must drop off to great depths very quickly. This is necessary because a large portion of the electricity generated by an OTEC system is used internally to pump the cold water up from the depths of the ocean. The longer the cold water pipe, the more electricity it takes to pump the cold water to the OTEC facility, and the lower the net electrical output of the power plant. 

There are three potential types of OTEC power plants opcii-cyclc, closed-cycle, and hybrid systems. Open-cycle OTEC systems exploit the fact that water boils at temperatures below its normal boiling point when it is under lower than normal pressures. Open-cycle systems convert warm surface water into steam in a partial vacuum, and then use this steam to drive a large turbine connected to an electrical generator. Cold water piped up from deep below the oceans surface condenses the steam. Unlike the initial ocean water, the condensed steam is desalinated (free of salt) and may be collected and used for drinking or irrigation. 

Access for air into the boiler house must be considered. Air for combustion will be drawn in through purpose-made louvers and care should be taken that this air does not create a hostile environment to personnel in the building. Also, passage of air across cold water pipes should be avoided, as in cold weather this may aggravate freezing in the pipes. 

Chlorinated poly (vinyl chloride) (CPVC) has increased Tg compared to PVC, and this increases its upper use temperature. Applications include hot- and cold-water pipe as well as pipe for the handling of industrial chemical liquids. Chlorinated polyethylene (CPE) finds use as roofing and other vapor barrier membranes, as pond liners, and as an additive to improve the impact strength of PVC. 

One of the more ambitious underseas projects involving syntactic foam is a 23-ton flotation collar that provides 32 tons of buoyancy 46). The part, 5.5 m in diameter and 3 m long, encases cold-water pipes, in an oceanic thermal-energy conversion system being developed by the US Department of Energy it has been tested off the coast of Hawaii, at depths of 915 m. 

Ferrous oxide (FeO) and hydrated iron oxide (FeOOH) are found as bright red to red-brown light and fluffy deposits in cold water piping, cold wells, and well water makeup. 

GROUND ROD, COLD WATER PIPE, BUILDING STEEL GROUND RING, CONCRETE ENCASED ELECTRODE ETC. 

EXAMPLE 3-14 Heat Transfer between Hot- and Cold-Water Pipes... 

I A -m-lopg section of hot- and cold-water pipes lun parallel to each other in a I thick concrete layer, as shown in Fig. 3-50. The diameters of both pipes are g 5 cm, and the distance between the centerline of the pipes is 30 cm. The sur-ti face temperatures of the hot and cold pipes are /O C and 15°C, respectively,... 

SOLUTION Hot- and cold-water pipes run parallel to each other in a thick concrete layer. The rate of heat transfer between the pipes is to be determined. Assumptions 1 Steady operating conditions exist. 2 Heat transfer is two-dimensional (no change in the axial direction). 3 Thermal conductivity of the concrete is constant. 

Discussion We can reduce this heat loss by placing the hot- and cold-water pipes further away from each other. 

Suppose you run water into a bathtub. You control the temperature of the water by adjusting the flow from the hot and cold water pipes. When the streams mix, heat flows from the hot water to the cold water. You classify an object as hot or cold by whether heat flows from you to the object or from the object to you. The temperature of an object is a measure of how hot or cold the object is relative to other objects. 

A precipitation reaction that is a slight variation on the one depicted in Figures 4.8 and 4.9 helps explain why a solid scale forms more rapidly in your hot water pipes than in your cold water pipes. 

Traditional applications of CPVC compounds are hot and cold water distribution piping, fittings, and valves that can handle industrial liquids and chemicals. The increasing popularity of CPVC in its application in hot and cold water pipes in residential units stems from its continuous-use rating of 80°C (176°F) and 100 psi, its approval for potable water by the National Sanitation Foundation (U.S.A.), and its low heat loss along with lack of sweating and scale buildup. 

When copper piping is used in tap water systems, one will, particularly in hot water pipes, and also in cold water pipes in periods with little or no tapping, get an increased concentration of copper ions, sometimes to a great extent. After tapping of such water into containers, pots or pans of less noble metals (e.g. aluminium), copper is deposited, and heavy pitting corrosion may occur. 

FIGURE 5 Types of flexible joints studied for OTEC CWP support. [From TRW (1979). Ocean Thermal Energy Conversion Cold Water Pipe Preliminary Design Final Report. TRW Energy Systems Group.]... 

Cold Water Pipes for Shore-Based Plants... 

Buoyant polyethylene (HDPE) cold water pipes of 1 m in diameter, anchored at intervals with cables attached to weights on the sea bottom, have been constmcted and deployed at NELHA and are operating successfully. FRP pipes suitable for shore-based plants of several megawatts seem feasible. A preliminary engineering design is available of water ducts for a 50-MWe OTEC plant using concrete ducts for cold deep water, warm surface water, and mixed exhaust water. 

Cold water pipe system 73.1 Biofouling corrosion control 0.3... 

Uses Pipe, profile and sheet extrusion calendering inj. molding hot and cold water pipe hot water plumbing components waste disposal devices automotive interior parts pumps construction applies. business and telecommunications applies. chem. handling equip. industrial liquid handling Manuf./Distrib. Noveon http //www.noveoninc. com, http //WWW. carbopol. com, http //www.noveoncoatings. com Trade Name Synonyms Lucalor CPVC [Atofina http //www.atofinachemicals.com, Atofina SA http //WWW. atofina. com]... 

A disadvantage of Portland cement coatings is the sensitivity to damage by mechanical or thermal shock. Open tanks are easily repaired, however, by troweling fresh cement into cracked areas. There is evidence that small cracks in cold-water piping are automatically plugged with a protective reaction product of rust combining with alkaline products leached from the cement. In sulfate-rich waters, Portland cement may be attacked, but cement compositions are now available with improved resistance to such waters. 

All the metal parts (pump, hot piping, condenser tubes etc are made of Hastelloy C-276 or equivalent after testing the corrosion resistance) The valves and cold water piping could be made of polypropylene or high-density polyethylene. 

The temperature of a metal exposed to the atmosphere is sometimes lower than that of the air itself. A well know example is the condensation of water on the outside wall of a poorly insulated cold water pipe. The same phenomenon may occur when a car that was previously exposed to cold air is parked in a heated garage. 

Amongst the stainless steels, ferritic Cr steels and the austenitic CrNi steels with and without added molybdenum must be considered as passivatable materials for domestic installations. These materials are of particular interest for hot water pipes and hot water tanks, as well as for cold water pipes. The stainless steels suitable for domestic installations are summarised in Table 16. 

System grounds can be derived from a ground attachment to a cold-water pipe ahead of the water meter or by a system of ground electrodes or some combination of these. A single ground point for the system should be established and periodically checked for continuity. Provision should be made to disconnect the system neutral during tests. 

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