scholarly journals Stearic Acid/Inorganic Porous Matrix Phase Change Composite for Hot Water Systems

Molecules ◽  
2019 ◽  
Vol 24 (8) ◽  
pp. 1482 ◽  
Author(s):  
Ling Xu ◽  
Rui Yang
Keyword(s):  
Dynamic Response ◽  
Stearic Acid ◽  
Phase Change ◽  
Heat Storage ◽  
Waste Heat ◽  
Porous Matrix ◽  
Water Systems ◽  
Hot Water ◽  
Cyclic Stability

The storage and utilization of waste heat in low and medium temperature ranges using phase change materials (PCMs) is an effective technology to improve energy utilization efficiency in combined cooling, heating, and power (CCHP) systems. In this paper, stearic acid/inorganic porous matrix phase change composites were developed to store waste heat for hot water systems. Among them, stearic acid/expanded graphite (EG) phase change composite was highlighted and the thermal physical properties, the dynamic response, and the long-term cyclic stability were evaluated. The stearic acid concentrations in the composites were over 95 wt%. The thermal diffusion coefficients were 3–5 times higher than pure stearic acid, independent of composite densities. Accordingly, the heat storage and release times were decreased by up to 41% and 55%, respectively. After 100 cycles, the composites maintained good dynamic response and long-term cyclic stability, with heat storage density of 122–152 MJ/m3. Hence, this stearic acid/EG phase change composite exhibits excellent comprehensive performances. It is also easy to be prepared and flexible for various types of heat exchangers.

scholarly journals Long-term heat-storage ceramics absorbing thermal energy from hot water

2020 ◽  
Vol 6 (27) ◽  
pp. eaaz5264
Author(s):  
Yoshitaka Nakamura ◽  
Yuki Sakai ◽  
Masaki Azuma ◽  
Shin-ichi Ohkoshi
Keyword(s):  
Thermal Energy ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Heat Storage ◽  
Waste Heat ◽  
External Pressure ◽  
Heat Energy ◽  
Hot Water

In thermal and nuclear power plants, 70% of the generated thermal energy is lost as waste heat. The temperature of the waste heat is below the boiling temperature of water. Here, we show a long-term heat-storage material that absorbs heat energy at warm temperatures from 38°C (311 K) to 67°C (340 K). This unique series of material is composed of scandium-substituted lambda-trititanium-pentoxide (λ-ScxTi3−xO5). λ-ScxTi3−xO5 not only accumulates heat energy from hot water but also could release the accumulated heat energy by the application of pressure. λ-ScxTi3−xO5 has the potential to accumulate heat energy of hot water generated in thermal and nuclear power plants and to recycle the accumulated heat energy on demand by applying external pressure. Furthermore, it may be used to recycle waste heat in industrial factories and automobiles.

Long term durability of crosslinked polyethylene tubing used in chlorinated hot water systems

1999 ◽  
Vol 28 (6) ◽  
pp. 309-313 ◽  
Author(s):  
T.S. Gill ◽  
R.J. Knapp ◽  
S.W. Bradley ◽  
W.L. Bradley
Keyword(s):  
Water Systems ◽  
Hot Water ◽  
Polyethylene Tubing

Review of the application of phase change material for heating and domestic hot water systems

2015 ◽  
Vol 42 ◽  
pp. 557-568 ◽  
Author(s):  
M.K. Anuar Sharif ◽  
A.A. Al-Abidi ◽  
S. Mat ◽  
K. Sopian ◽  
M.H. Ruslan ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Water Systems ◽  
Hot Water ◽  
Domestic Hot Water ◽  
Change Material

scholarly journals Comparison of Short-Term Testing and Long-Term Monitoring of Solar Domestic Hot Water Systems

1987 ◽  
Vol 109 (4) ◽  
pp. 274-280
Author(s):  
S. B. Beale
Keyword(s):  
Water Systems ◽  
Hot Water ◽  
Testing Time ◽  
Short Term ◽  
Solar Simulator ◽  
Good Correspondence ◽  
Domestic Hot Water ◽  
Solar Fraction ◽  
Load Schedule

This paper reports on the results of a comparison between short-term indoor testing and long-term outdoor monitoring of solar domestic hot water systems. Five solar-preheat systems were monitored under side-by-side conditions of irradiance and load, for a period of two years. The systems were then tested according to a standard day test, using a solar simulator, and a load schedule identical to that imposed on each system during the monitoring. The systems were found to deliver 19.7 MJ–25.8 MJ daily in the test, compared to a two-year average of 19.1 MJ–26.0 MJ (1.5 to 2.0 GJ/m2 annually) outdoors. System rank was reasonably well preserved. Comparison of results on the basis of efficiency and solar fraction suggests that good correspondence exists between long-term outdoor results and those of indoor testing, at least for systems with stable controllers. Selected systems were also tested at different load schedules and radiation levels. Methods of predicting the performance of a solar-preheat system from the results of a standard day test are discussed, and the possibility of reducing testing time to a single day is explored.

An Improvement in the Solar Water Heating Systems by Thermal Storage Using Phase Change Materials

Solar Energy ◽  
2006 ◽  
Author(s):  
D. Vikram ◽  
S. Kaushik ◽  
V. Prashanth ◽  
N. Nallusamy
Keyword(s):  
Phase Change ◽  
Solar Collector ◽  
Storage Tank ◽  
Phase Change Materials ◽  
Heat Storage ◽  
Control Device ◽  
Hot Water ◽  
Water Heater ◽  
Storage Unit ◽  
Solar Water

The present work has been undertaken to study the feasibility of storing solar energy using phase change materials (like paraffin) and utilizing this energy to heat water for domestic purposes during nighttime. This ensures that hot water is available through out the day. The system consists of two simultaneously functioning heat-absorbing units. One of them is a solar water heater and the other a heat storage unit consisting of Phase Change Material (PCM). The water heater functions normally and supplies hot water during the day. The storage unit stores the heat in PCMs during the day and supplies hot water during the night. The storage unit utilizes small cylinders made of aluminium, filled with paraffin wax as the heat storage medium and integrated with a Solar Collector to absorb solar heat. At the start of the day the storage unit is filled with water completely. This water is made to circulate between the solar collector and the PCM cylinders. The water in the storage tank receives heat form the solar collector and transfers it to the PCM. The PCM undergoes a phase change by absorbing latent heat, excess heat being stored as sensible heat. The water supply in the night is routed to the storage unit using a suitable control device. The heat is recovered from the unit by passing water at room temp through it. As water is drawn from the overhead tank, fresh water enters the unit disturbing the thermal equilibrium, causing flow of heat from PCM to the water. The temperature of the heated water (outlet) is varied by changing the flow rate, which is measured by a flow meter. The storage tank is completely insulated to prevent loss of heat. The performance of the present setup is compared with that of a system using same PCM encapsulated in High Density PolyEthylene (HDPE) spherical shells.

scholarly journals Analysis of the Thermal Storage Performance of a Radiant Floor Heating System with a PCM

Molecules ◽  
2019 ◽  
Vol 24 (7) ◽  
pp. 1352 ◽  
Author(s):  
JinChul Park ◽  
TaeWon Kim
Keyword(s):  
Heat Storage ◽  
Waste Heat ◽  
Heating System ◽  
Hot Water ◽  
Current Status ◽  
Indoor Environments ◽  
Storage Performance ◽  
Radiant Floor Heating System ◽  
Radiant Floor Heating ◽  
Floor Heating

This study first reviewed previous studies on floor heating systems based on the installation of a phase change material (PCM) and the current status of technical developments and found that PCM-based research is still in its infancy. In particular, the improvement of floor heat storage performance in indoor environments by combining a PCM with existing floor structures has not been subject to previous research. Thus, a PCM-based radiant floor heating system that utilizes hot water as a heat source and can be used in conjunction with the widespread wet construction method can be considered novel. This study found the most suitable PCM melting temperature for the proposed PCM-based radiant floor heating system ranged from approximately 35 °C to 45 °C for a floor thickness of 70 mm and a PCM thickness of 10 mm. Mock-up test results, which aimed to assess the performance of the radiant floor heating system with and without the PCM, revealed that the PCM-based room was able to maintain a temperature that was 0.2 °C higher than that of the room without the PCM. This was due to the rise in temperature caused by the PCM’s heat storage capacity and the emission of waste heat that was otherwise lost to the underside of the hot water pipe when the PCM was not present.

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