Cold water modeling

In the North American market, water heaters are almost always made with the cold water inlet and hot water outlet lines coming out of the top of the tank. The hot water outlet opens right into the top of the tank and so draws off the hottest water. The hot water has risen to the top of the tank because of its lower density. The cold water on the inlet side is directed to the bottom of the tank by a plastic dip-tube. In some models the dip-tube is curved or bent at the end to increase the turbulence at the bottom of the tank. This is to keep any sediment from settling on the bottom of the tank. As sediment— usually calcium carbonate or lime—precipitated out of the water by the increased temperature builds up, it will increase the thermal stress on the bottom of a gas-fired water heater and increase the likelihood of tank failure. On electric water heaters the sediment builds up on the surface of the elements, especially if the elements are high-density elements. Low-density elements spread the same amount of power over a larger surface of the element so the temperatures are not as high and lime doesn t build up as quickly. If the lower elements get completely buried in the sediment, the element will likely overheat and burn out. 

The other example concerns the installation of separate faucets for hot and cold water when mixing faucets had been requested. The laboratory operator would have caught this had he checked faucet model numbers on the drawings. 

N. M. To, H. M. Brown, and R. H. Goodman. Data analysis and modeling of dispersant effectiveness in cold water. In Proceedings Volume, pages 303-306. 10th Bien API et al Oil Spill (Prev, Behav, Contr, Cleanup) Conf (Baltimore, MD, 4/6-4/9), 1987. 

The GC-TEA conditions used for the detection of volatile nitrosamines have been described by Fine and Rounbehler (8). A 14 x 1/8" stainless steel column packed with 5% Carbowax 20M containing 2% NaOH on Chromosorb W HP (80-100 mesh) was operated at 175°C with argon gas as the carrier at a flow rate of 15 mL/min. A TEA was used as the detector with dry ice/ethanol as the cold trap. The HPLC-TEA was constructed by sequentially connecting a high pressure pump (Altex, model 110), an injector (Waters, model U6K), a yPorasil column (Waters), and a TEA. The operation of HPLC-TEA has been described by Fine, et al.( ). 

To a good first approximation, the Great Lakes fit a model involving the equilibrium of calcite, dolomite, apatite, kao-Unite, gibbsite, Na- and K-feldspars at 5°C., 1 atm. total pressure with air of PCo2 = 3.5 X 10" atm. and water. Dynamic models, considering carbon dioxide pressure and temperature as variables (but gross concentrations fixed), show that cold waters contain excess carbon dioxide and are unsaturated with respect to calcite, dolomite, and apatite, whereas warm waters are nearly at equilibrium with the atmosphere but somewhat supersaturated with respect to calcite, dolomite, and apatite. 

Figure 4.18 Upper right figure shows a forced-draft or blowthrough tower, which has a fan at the bottom for driving air through the fill above, Tower selection for smaller units can be made from the accompanying curves and table for a cold water temperature of 85°F (this is generally the water basin discharge temperature for small towers). As an example, enter at 104°F hot water temperature to a wet bulb value of 75°F, then drop vertically to the water flow selected (580 gpm). This falls between curves that designate the manufacturer s distinct model size. Select the next larger size, i,e., the curve immediately below, and follow across to the recommended tower model).

Equilibria among water ice, liquid water, and water vapor are critical for model development because these relations are fundamental to any cold aqueous model, and they can be used as a base for model parameterization. For example, given a freezing point depression (fpd) measurement for a specific solution, one can calculate directly the activity of liquid water (or osmotic coefficient) that can then be used as data to parameterize the model (Clegg and Brimblecombe 1995). These phase relations also allow one to estimate in a model the properties of one phase (e.g., gas) based on the calculated properties of another phase (e.g., aqueous), or to control one phase (e.g., aqueous) based on the known properties of another phase (e.g., gas). 

Experimental. A Parr model 1221 oxygen bomb calorimeter was modified for isothermal operation and to ensure solution of nitrogen oxides (2). The space between the water jacket and the case was filled with vermiculite (exploded mica) to improve insulation. A flexible 1000-watt heater (Cenco No. 16565-3) was bent in the form of a circle to fit just within the jacket about 1 cm. above the bottom. Heater ends were soldered through the orifices left by removing the hot and cold water valves. A copper-constantan thermocouple and a precision platinum resistance thermometer (Minco model S37-2) were calibrated by comparison with a National Bureau of Standards-calibrated Leeds and Northrup model 8164 platinum resistance thermometer. The thermometer was used to sense the temperature within the calorimeter bucket the thermocouple sensed the jacket temperature. A mercury-in-glass thermoregulator (Philadelphia Scientific Glass model CE-712) was used to control the jacket temperature. 

Example 4.13. Carbon-14 as a Tracer for Oceanic Mixing In a simplified two-box model of the ocean, the warm waters and the cold waters may tie subdivided into two well-mixed reservoirs—an upper one a few hundred meters in depth and a lower one of 3200 m depth. The Cj content of the upper and lower reservoirs (corresponding to the Pacific) are, respectively, 1.98 x 10 mol liter and 2.44 x 10 mol liter, whereas the C/C ratios for uppsr and lower reservoirs are, respectively, 0.92 x 10 and 0.77 x 10 mol/ mol. Estimate from this information the rate of vertical mixing and the residence time of the water in the deep sea (Broecker, 1974). 

We conducted cold flow model experiments in a air-water/glycerin system to investigate a cause of maldistribution in a catalyst bed. The apparatus used was a 30 cm I.D. acrylic column equipped with a liquid distributor at the top and a liquid collector with 33 compartments at the bottom. Bed depth can be varied by combining the pipes. Liquid distribution at a given depth of the bed was estimated by measuring the liquid flow from each compartment of the collector. We examined effects of gas and liquid velocity, liquid viscosity, particle shapes, and ways of catalyst loading on liquid distribution in the bed. An increase in liquid velocity or viscosity slightly improved liquid distribution. However, gas flow rate did not affect liquid distribution. 

There are many instances where the results of one study have not been confirmed by the results of another study using the same chemical. Such disturbing discrepancies may be explained in part by differences in protocol for chemical administration (food, ambient water or injection) or dose or duration of the treatment. Furthermore, over 30 different model species from marine, freshwater, tropical, temperate and cold-water environments have been used. Also, fish have rarely been at a comparable physiologic state or stage of development or maturation and have been held under diverse environmental conditions. If indeed, as seems to be the case, variations in thyroidal responses to ecotoxicants can be explained in part by variations in species, environmental conditions and physiologic state, then selection of a standardized... 

Fig. 7. Stylized temperature dependent growth model for hypothetical warm water and cold water species (Schmidt et al. 2006) based on Bradshaw (1961). The environmental niche is dived into optimum growth, a reproductive range, the minimum temperature for growth and the physiological limit leading to lethal conditions.

The model domain boundary was chosen so that the model area is significantly larger than the volume of the heated zone, and it includes the cold water recharge zone as well. 

It can be seen by the temperature distribution (Fig. 5) that cold water from peripheral parts of the model are immersing with a simultaneous heating from the local thermal source. Hot water is discharged to a well-penetrable sub-fluvial alluvium of the Paratoonka river. 

Xanthan gum dissolves in either hot or cold water to produce high viscosity solutions at low concentration. The relationship between viscosity and concentration is shown in Figure 3. Xanthan gum has a viscosity of approximately 300 cP at a concentration of 0.5% and 1400 cP at a concentration of 1.0% when measured at 60 rpm with a Brookfield Model LVF viscometer at -25C. 

The absorption of a gas during condensation of water vapor on a cold water droplet Is a complex process characterized by unsteady state mass and heat transfer [6]. In the classical development of absorption of a gas In a liquids three theoretical models have ensued The film theory, the penetration theory, and the boundary layer theory. Each model Invokes different assumptions which result in different conclusions. 

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