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Constructions and related matters relevant to environmental health
Published in Stephen Battersby, Clay's Handbook of Environmental Health, 2023
John Bryson, Stephen Battersby
Cooling towers have been used as part of air conditioning and are heat removal devices used to transfer process waste heat to the atmosphere. They may either utilise the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb temperature or rely on air to cool the working fluid to near the dry-bulb temperature. Wet-bulb temperature is the lowest temperature that can be reached by the evaporation of water only. It is the temperature felt when your skin is wet and is exposed to moving air. Wet-bulb temperature is an indication of the amount of moisture in the air. Dry-bulb temperature is the temperature of air measured by a thermometer freely exposed to the air but shielded from radiation and moisture. It is the temperature usually considered as air temperature and is the true thermodynamic temperature.
The Auditor’s Tools and How to Use Them
Published in Stan Harbuck, Donna Harbuck, Residential Energy Auditing and Improvement, 2021
To determine relative humidity, a sling psychrometer can be used, although a simple indoor/outdoor thermometer (Figure 4-4) that provides relative humidity can be accurate enough for your purposes and is a lot less fragile than a sling psychrometer. A sling psychrometer is basically two thermometers side-by-side, one has a cotton wick that has been wetted around the bulb of the thermometer (wet bulb), and the other is open to air (dry bulb). By spinning the sling psychrometer in the air long enough, the temperature stabilizes. When the wet bulb temperature stabilizes, you have found the wet bulb temperature. The dry bulb temperature is like the regular air temperature taken with a thermometer while the wet bulb temperature is what the temperature would be if, say, you wet your finger and held it to the wind. You can take these two temperatures and place them on a psychometric chart to determine dew point and relative humidity (see Appendix E).
Water Efficiency
Published in Steve Doty, Commercial Energy Auditing, 2020
The refrigeration cycle of mechanical cooling systems are almost universally more efficient when cooled with water rather than air. Once through water cooling allows condensing temperatures near the temperature of the water source which may be city water, river water, sea water, etc. When city water is used, once through water cooling is expensive and places large demands upon local water supplies so, to conserve water, most cooling systems use a cooling tower which evaporates a portion of the water to cool the rest of the water. With a cooling tower, the water temperature is a function of wet bulb temperature which is lower than dry bulb temperature. The amount of savings over air-cooled systems depends upon the wet bulb depression, which is determined from weather tables for the given location (psychrometrics). Aiding the saving of water-cooled systems are the reduced heat exchanger approach values compared to tube-in-air heat exchangers and higher economizer hours where cooling occurs without a compressor. Subtracting from the savings of water-cooled systems are the ancillary pumps used to move the water around. Specific power for a cooling tower fan is similar to that of an air-cooled condenser.
Empirical modelling of variable capacity air-to-air heat pumps in trnsys
Published in Journal of Building Performance Simulation, 2022
Gregor Strugala, Michaël Kummert, Martin Kegel
This section proposes a method to fill this missing information. The first step is to use the cooling performance corrections presented in Figures 10 and 11 that allow to determine the total cooling capacity . Then, the sensible and latent capacities ( and ) are deduced from the sensible heat ratio (shr), which can be defined as . A regression from experimental data allows to compute the shr from the wet-bulb depression . This quantity is convenient because the wet-bulb temperature is generally the variable used to quantify humidity in manufacturer tables. It shows the degree of humidity saturation in the return air, so that the shr is close to zero at low values, and as (Figure 14). The shr regression has the following form: This correlation may not be adapted to every heat pump model, but it allows to model the shr variation with indoor humidity in the absence of sufficient performance data.
Innovative configuration of a hybrid nuclear-parabolic trough solar power plant
Published in International Journal of Sustainable Energy, 2018
Once installed, the condenser performance is affected by many factors including cooling water inlet temperature, cooling water flow rate, condenser thermal load, tubes fouling and the amount of air leaking into the condenser. The cooling water inlet temperature itself depends on the cooling tower functioning. The performance of the cooling tower is predetermined by the air wet bulb temperature (Black & Veatch 1996). The wet bulb temperature represents the lowest temperature at which the circulating water can be cooled in the tower. Since there are inefficiencies in the cooling tower evaporative cooling process, the cooling tower can only cool to within an approach of the wet bulb temperature. As a result, for a given cooling tower, the cold water temperature decreases as the wet bulb temperature drops.
Theoretical and experimental study of the multistage dynamic dehumidifier for enhanced thermal comfort conditions in a building
Published in Journal of Building Performance Simulation, 2022
Sampath Suranjan Salins, S.V. Kota Reddy, Shiva Kumar
Digital thermometers measure the dry bulb temperatures. Wet bulb temperature is measured using the thermometer where the bulb is wound with a soaked cloth. This measures the temperature of the saturated air. Hygrometer measures the relative humidity, airflow rate is measured using an anemometer, clamp metre measures the instant voltage and current and energy metre measures the total energy consumed by the system. Tachometer measures the camshaft speed, and the concentration of the desiccant is measured using refractometer. Flowmeter measures the desiccant flow rate. Table 2 lists the details of all the instruments with their specification, resolution and accuracies.