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Special Systems
Published in Carl Bozzuto, Boiler Operator's Handbook, 2021
Hydronic heating systems must have provisions for thermal expansion. When water is heated from a nominal building temperature of 65°F to an operating temperature of 180°F, each cubic foot of water in the system will swell by almost 3%. That is not a lot percentage wise. However, when the total volume of a heating system is considered, that can be several hundred gallons. A plant that is water logged (all elements full of water) can experience extreme swings in pressure associated with the expansion and contraction of the water. An expansion tank is provided in a hydronic heating system to reduce pressure swings to a tolerable range.
Hydronic Distribution Equipment and Systems
Published in T. Agami Reddy, Jan F. Kreider, Peter S. Curtiss, Ari Rabl, Heating and Cooling of Buildings, 2016
T. Agami Reddy, Jan F. Kreider, Peter S. Curtiss, Ari Rabl
An expansion tank is an essential component for closed systems; its thermal function is to allow water to expand into a designated airspace to avoid high stresses that would otherwise occur in a piping system if no such air space for water expansion existed. Unconfined water expands almost linearly with temperature in the range of temperatures encountered in HVAC systems. For example, water expands about 2% between 40°F and 150°F (5°C and 65°C); it expands a little more than 3% between 40°F and 200°F (5°C and 94°C). Expansion tanks are needed in all closed systems, but not in systems open to the atmosphere.
Domestic Water Heating
Published in William C. Dickinson, Paul N. Cheremisinoff, Solar Energy Technology Handbook, 2018
Figure 27.6 shows a two-pump system with an external double-walled heat exchanger. The collector fluid is either a glycol-water antifreeze mixture or a silicone oil type of liquid. Both pumps are turned on when solar heat can be collected. The expansion tank is necessary to accommodate volume changes in a closed system with temperature. It is very important to pressurize closed loop systems to about 10 psig to prevent pump cavitation and burnout. Also inline air separators aid in initial filling and startup of the system.
Westinghouse Test Facilities for Lead Fast Reactor Development
Published in Nuclear Technology, 2023
Sung Jin Lee, Michael Ickes, Jeffrey L. Arndt, Michael Epstein, Asfaq Patel, Paolo Ferroni
The expansion vessel adjoins the test loop portion of the facility and is intended to allow for the presence of cover gas over the lead (supporting oxygen control) and to allow for thermal expansion of the lead. Similar to the storage tank, the expansion tank volume is 15% to 20% larger than the coolant inventory, 200 L, to allow for the thermal expansion of the lead. The operating parameters of the expansion tank are design temperature: 650°Coperating temperature: 600°Cdesign pressure: 3 bargoperating pressure: 0.1 barg.
Experimental and numerical studies on natural circulation behavior of heat exchanger for molten salt loop
Published in Journal of Nuclear Science and Technology, 2020
Yanhua Wu, Chuangxiong Cai, Kai Wang, Xiaowei Jiao, Qun Yang, Zhaozhong He, Kun Chen
A schematic of the NNCL is presented in Figure 1, and the parameters of the main measuring instruments are displayed in Table 1. The NNCL employs HTS-1 (KNO3-NaNO2-NaNO3 (53-40-7 wt%)) as the coolants. It consists of a molten salt tank, a transport tank, an ultrasonic flow meter, a chimney, two heat exchangers (DHX and NDHX), an electric heater, several thermocouples, various pressure gauges, and a number of valves. The critical parameters are presented in Table 2. The heaters are made of wires, evenly jacketed on the outside surface of the molten salt tank to produce heat, which is the driving force of the NNCL, as with the heat from the reactor core. The maximum power of the heaters can reach 50 kW. An expansion tank is designed to be placed at the highest elevation of the natural circulation to allow for thermal expansion of the salt. The entire loop adopts superior-quality insulating cotton to provide excellent insulation effects and to reduce heat loss within the maximum limit.
Thermal-Hydraulic System-Level Analysis of a Molten Salt Natural Circulation Loop
Published in Nuclear Science and Engineering, 2023
Sheng Zhang, Hsun-Chia Lin, Xiaodong Sun
The FLiBe salt temperature predicted by NACCO is 11.5°C to 23.1°C higher than experimental data, as shown in Fig. 21a. There are three potential reasons for the large discrepancy between the code predictions and experimental data: (1) underestimate of the heat removal rate by the top cooler, (2) large difference between the mass-flow-weighted area-averaged temperatures (bulk mean temperatures) predicted by NACCO and salt pipe centerline temperatures measured in the experiments,19 and (3) heat losses from the two connecting tanks and associated piping—an expansion tank close to the inlet of the cooling section and another tank close to the outlet of the cooling section for material corrosion tests.