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| 2. |
- Chiu, Justin NingWei, et al.
(author)
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A Review of Thermal Energy Storage Systems with Salt Hydrate Phase Change Materials for Comfort Cooling
- 2009
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In: 11th International Conference on Thermal Energy Storage, June 14-17 , 2009, Stockholm, Sweden..
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Conference paper (peer-reviewed)abstract
- This paper presents a review of cold thermal energy storage technologies. Latent heat thermal energy storage (LHTES) with phase change materials (PCMs) deserves attention as they provide high energy density and small temperature change interval upon melting/solidifying. Salt hydrates are especially interesting since they demonstrate high latent heat of fusion, high thermal conductivity, low flammability, and facilitate the use in buildings as compared to organic PCMs. A review of system performance obtained from experimental work, theoretical analyses and real case studies has however shown some material shortcomings. To reach cost effectiveness, future work in the field of LHTES with salt hydrates lies in finding suitable methods for limiting incongruent melting and subcooling without compromising the storage density. Also, system integration of LHTES in cold applications can be further developed in terms of innovative design for high power and storage capacity, load optimized sizing, controls, and elimination of PCM encapsulation.
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| 3. |
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| 4. |
- Chiu, Justin NingWei, et al.
(author)
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System Integration of Latent Heat Thermal Energy Storage Systems for Comfort Cooling Integrated in district cooling network
- 2009
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In: 11th International Conference on Thermal Energy Storage, EFFSTOCK 2009, Stockholm, Sweden, June 14-17, 2009..
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Conference paper (peer-reviewed)abstract
- Latent heat thermal energy storage for comfort cooling with phase change materials (PCMs) has increasingly gained attention. For effective system integration, an optimized strategy for load shifting to cut down peak hour energy use is needed. With the focus on overall system performance, this paper addresses matching of a cold storage capacity and power to a demand while assessing the cost effectiveness of the PCM technology. A simulation model based on one office building cooling load in Stockholm Sweden was used. Storage capacity, power output and PCM cost were shown to be the predominant factors in a system design. It has been found that load leveling can cost effectively reduce the peak load by 5% to 9% in a fixed tariff system. However, with 50% reduction in today’s PCM price combined with removal of district cooling return temperature penalty, the peak power reduction rate may be increased to 30%.
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| 5. |
- He, Bo, et al.
(author)
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Phase transition temperature ranges and storage density of paraffin wax phase change materials
- 2004
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In: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 29:11, s. 1785-1804
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Journal article (peer-reviewed)abstract
- Paraffin waxes have been used in many latent thermal energy storage applications because of their advantageous thermal performances. In this paper, the liquid-solid phase diagram of the binary system of tetradecane and hexadecane has been used to obtain information of the phase transition processes for cool storage applications. The analysis of the phase diagram indicates that, except for the minimum-melting point mixture, all mixtures melt and freeze in a temperature range and not at a constant temperature. The latent heat of fusion evolves throughout this temperature range. Differential scanning calorimetry (DSC) was used to determine the thermophysical properties of the binary system. Depending on the DSC settings throughout the measurements, varying results were obtained. For example, when the DSC runs at a high heating/cooling rate, it will lead to erroneous information. Also, the correct phase transition temperature range cannot be obtained simply from DSC measurement. By combining phase equilibrium considerations with DSC measurements, a reliable design method to incorporate both the heat of phase change and the temperature range is presented.
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| 6. |
- Iwata, S., et al.
(author)
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Therapeutic hypothermia can be induced and maintained using either commercial water bottles or a "phase changing material'' mattress in a newborn piglet model
- 2009
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In: Archives of Disease in Childhood. - : BMJ. - 0003-9888 .- 1468-2044. ; 94:5, s. 387-391
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Journal article (peer-reviewed)abstract
- Background: Therapeutic hypothermia, a safe and effective treatment for neonatal encephalopathy in an intensive care setting, is not available in low-resource settings. Aims/Methods: To assess two low-tech, low-cost cooling devices for use in low-resource settings: (i) commercially available water bottles filled with tepid water (25 degrees C); (ii) a mattress made of phase changing material (PCM) with a melting point of 32 degrees C (PCM works as a heat buffer at this temperature). Eleven anaesthetised newborn piglets were studied following transient hypoxia-ischaemia. The cooling device was applied 2-26 h after hypoxia-ischaemia with a target rectal temperature (T-rectal) of 33-34 degrees C. T-rectal undershoot was adjusted using cotton blankets; the cooling device was renewed when T-rectal rose above 35 degrees C. T-rectal data during cooling were dichotomised (within or without target) to assess: (a) the total period within the target T-rectal range; (b) the stability and fluctuation of T-rectal during cooling. Results: Therapeutic hypothermia was achieved with both water bottles (n=5) and the PCM mattress (n=6). The mean (SD) time to reach target T-rectal was 1.8 (0.5) h with water bottles and 1.9 (0.3) h with PCM. PCM cooling led to a longer period within the target T-rectal range (p<0.01) and more stable cooling (p<0.05). Water bottle cooling required device renewal (in four out of five piglets). Conclusion: Simple, low-tech cooling devices can induce and maintain therapeutic hypothermia effectively in a porcine model of neonatal encephalopathy, although frequent fine tuning by adjusting the number of blankets insulating the piglet was required to maintain a stable temperature. PCM may induce more stable cooling compared with water bottles.
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| 7. |
- Martin, Viktoria, et al.
(author)
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Compact Heat Storage for Solar Heating Systems
- 2009
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In: Journal of solar energy engineering. - : ASME International. - 0199-6231 .- 1528-8986. ; 131:4
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Journal article (peer-reviewed)abstract
- Energy and cost efficient solar hot water systems require some sort of integrated storage, with high energy density and high power capacity for charging and discharging being desirable properties of the storage. This paper presents the results and conclusions from the design, and experimental performance evaluation of high capacity thermal energy storage using so-called phase change materials (PCMs) as the storage media. A 140 l 15 kW h storage prototype was designed, built, and experimentally evaluated. The storage tank was directly filled with the PCM having its phase change temperature at 58 degrees C. A tube heat exchanger for charging and discharging with water was submerged in the PCM. Results from the experimental evaluation showed that hot water can be provided with a temperature of 40 degrees C for more than 2 h at an average power of 3 kW. The experimental results also show that it is possible to charge the 140 l storage with close to the theoretically calculated value of 15 kW h. Hence, this is a PCM storage solution with a storage capacity of over 100 kW h/m(3), and an average power capacity during discharging of over 20 kW/m(3). However, it is desirable to increase the heat transfer rate within the prototype. A predesign of using a finned-tube coil instead of an unfinned coil show that by using finned tube, the power capacity for discharging can be at least doubled, if not tripled.
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| 8. |
- Martin, Viktoria, et al.
(author)
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Direct contact PCM-water cold storage
- 2010
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In: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 87:8, s. 2652-2659
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Journal article (peer-reviewed)abstract
- Comfort cooling demand continues to increase throughout the world Conventional cooling production results in high demand for electrical power during peak hours, leading to high emissions for producing cooling, and potential power shortages in electric grids With a cold storage, the peak power demand is effectively managed and enables free-cooling. This paper examines one concept using phase change materials (PCM) for storing of cold, where the cold carrier (water) is in direct contact with the PCM. This is in order to enable high power for charging and discharging while providing a high storage capacity. A theoretical model highlights important design parameters for reaching large storage and power capacity The capacity increases with the Packing Factor and temperature difference across the storage. For high power, the flow rate, temperature difference, and drop size is important parameters which is also verified in an experimental evaluation. The obtainable power is between 30 and 80 kW/m(3) storage Practical limitations of this concept are shown to be PCM-water bed expansion and non-uniform channeling due to asymmetric and unstable PCM shells.
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| 9. |
- Martínez, Joaquín, et al.
(author)
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Gas-phase controlled convective drying of solids wetted with multicomponent liquid mixtures
- 1991
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In: Chemical Engineering Science. - 0009-2509 .- 1873-4405. ; 46:9, s. 2235-2252
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Journal article (peer-reviewed)abstract
- The nonisothermal convective drying of an impermeable solid substrate covered with multicomponent solvent mixtures was studied. The aim was to simulate the nonsteady-state evaporation process under the control of the gas side heat and mass transfer. Diffusional resistances in the liquid layer were prevented by choosing conditions providing low evaporation rates. Evaporation fluxes were calculated by assuming either interactive or independent diffusion through the gaseous boundary layer. The interactive effects were accounted for by applying the linearized theory of Toor. Independent fluxes were calculated using the effective diffusivity method. In the experimental part, a Teflon substrate wetted with the binary mixture acetone—methanol, the ternary mixture ethanol—methylethylketone—toluene and the quaternary mixture ethanol—methanol—acetone—chloroform was dried using air flowing parallel to the evaporation surface as drying agent. Good agreement was obtained between experiments and simulations. Calculations show that liquid composition, liquid temperature, gas composition and diffusional interactions have a significant influence on the instantaneous selectivity while the effect of gas temperature and gas velocity is less important. Selectivity can be controlled by using a gas preloaded with an appropriate composition. The model can be applied to the drying, at an initial stage, of coated laminates with a gentle drying regime.
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| 10. |
- Martínez, Joaquín, et al.
(author)
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Non-isothermal convective drying of solids wetted with multicomponent liquid mixtures
- 1992
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In: Technology Today. - : Academy of Sciences of the Czech Republic. - 0862-9706. ; 2, s. 70-77
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Journal article (peer-reviewed)abstract
- The non-isothermal convective drying of an impermeable solid substrate covered with multicomponent solvent mixture was studied. The aim was to simulate the nonsteady-state evaporation process under the control of both the gas side heat and mass transfer, and in the presence of diffusional resistances in the liquid layer. Diffusional interactions in both phases were accounted for by applying the generalized Fick's formulation of diffusion with a temperature and composition dependent matrix of multicomponent diffusivities. In the experimental part, a teflon substrate covered with the ternary mixture ethanol-methylethylketone-toluene was dried using air flowing parallel to the evaporation surface as drying agent. Good agreement was obtained between experiments and simulations. Calculations show that liquid composition, liquid temperature, gas composition and diffusional interactions have a significant influence on the instantaneous selectivity while the effect of gas temperature and gas velocity is less important. Selectivity can be controlled by using a gas preloaded with an appropriate composition.
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| 11. |
- Olson, Linus, et al.
(author)
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Phase-Changing Glauber Salt Solution for Medical Applications in the 28-32 degrees C Interval
- 2021
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In: Materials. - : MDPI AG. - 1996-1944. ; 14:23
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Journal article (peer-reviewed)abstract
- (1) Background: The field of medicine requires simple cooling materials. However, there is little knowledge documented about phase change materials (PCM) covering the range of 28 to 40 degrees Celsius, as needed for medical use. Induced mild hypothermia, started within 6 h after birth, is an emerging therapy for reducing death and severe disabilities in asphyxiated infants. Currently, this hypothermia is accomplished with equipment that needs a power source and a liquid supply. Neonatal cooling is more frequent in low-resource settings, where ~1 million deaths are caused by birth-asphyxia. (2) Methods: A simple and safe cooling method suitable for medical application is needed for the 28 to 37.5 degrees C window. (3) Results: Using empirical experiments in which the ingredients in Glauber salt were changed, we studied the effects of temperature on material in the indicated temperature range. The examination, in a controlled manner, of different mixtures of NaCl, Na2SO4 and water resulted in a better understanding of how the different mixtures act and how to compose salt solutions that can satisfy clinical cooling specifications. (4) Conclusions: Our Glauber salt solution is a clinically suited PCM in the temperature interval needed for the cooling of infants suffering from asphyxia.
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| 12. |
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| 13. |
- Wang, Weilong, 1978-
(author)
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Preparation and performance of energy storage materials and application for recovery of industrial waste heat
- 2009
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Licentiate thesis (other academic/artistic)abstract
- Due to the rapid increase of energy consumption and the environmental concerns on climate change caused by the fossil fuel combustion, it becomes a big issue on how to use alternative renewable energy resources to replace fossil fuel and to improve energy utilization efficiency. In Sweden, there are plenty of detached buildings without connection with district heating (DH) network, which use oil to supply the hot water for space heating and tap water. One way is to extend the district heating network for supply the heat for the detached houses. However, this will need increased costs for the district heat pipeline which might not be economically variable for the area with less density of population. Another alternative is to apply so called mobilized thermal energy storage (M-TES) to transport heat from, e.g. industrial waste heat, to the end-users of the detached houses. This will enable to keep the detached houses in the same state as a distributed heat system while replacing the fossil fuels for heating demand. The mechanism of energy storage and release is on the basis of transition of phase change materials (PCMs), which can solve the problem in time and spatial mismatch between the energy supply and consumption. Polyethylene glycol (PEG) as a type of organic PCMs is studied in this licentiate thesis due to its large heat capacity and multi-melting temperatures. As a representative of organic PCMs, PEG also has some disadvantages, like encapsulation needed for preventing leakage and low thermal conductivity. To resolve those, a type of so-called form-stable energy storage materials is prepared by blending PEG with silica gel. Modified aluminium nitride (AlN) powder is then added to enhance the thermal conductivity of materials. Meanwhile, another form-stable energy storage material is prepared by mixing the melted PEG into expanded graphite (EG). The results show that two types of composite materials can keep the form stable during the transition, and AlN powder can enhance the thermal conductivities of energy storage materials. Based on the knowledge of energy storage technology, M-TES system is designed and combined with the existing heat system in Eskilstuna. The feasibility study of M-TES is carried out through the data collected from CHP plant and end-user in this licentiate thesis. The results show that there are economic and environmental benefits by using M-TES system to supply heat for detached houses.
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