Energy Storage Tank Research Articles

Turbulent buoyant flows into a two dimensional storage tank

A numerical model was developed to simulate the turbulent mixing processes that occur when a cold fluid flows into a two dimensional tank containing a warmer fluid. The process simulates the charging of a chilled water thermal energy storage tank. The numerical model employs a transient stream function-vorticity formulation to predict the streamline and temperature distributions in the tank. The turbulent effect was modeled by a two equation turbulent model using the turbulent kinetic energy and turbulent length scale equations. The results for a lower corner inlet flow show that the cold fluid will not extensively mix with the warmer fluid in the tank for Archimedean number greater than five and inlet Reynolds number less than 1000. The warm and cold fluids will thermally stratify under these conditions and limitations.

Exergy analysis of solar-assisted heat-pump systems for domestic heating

The exergetic efficiencies of solar-assisted heat-pump systems for domestic heating were investigated experimentally. The apparatus consists of 30 m 2 flat-plate, water-cooled solar collectors, a laboratory with 75 m 2 floor area to use as the conditioned area to be heated, a heat pump, a condenser, water-to-air and air-to-air evaporators, a latent heat thermal energy storage tank that is filled by encapsulated phase-change material (PCM), a water-to-air heat exchanger, a water-circulating pump, and other equipment. Experimental results were obtained for typical days during the months of December, January, February, March, April, and May for Trabzon. The experiments were made under clear-sky conditions for each month. The exergetic efficiencies are calculated using the experimental data and comparisons are made between the different systems.

Solar-assisted heat pump and energy storage for domestic heating in Turkey

In order to improve the performance of the solar-assisted heat pump system with energy storage for domestic heating in the Black Sea region of Turkey, an experimental set-up was constructed. In this study, the solar-assisted series heat pump system with storage and parallel heat pump system with storage are experimentally investigated and compared. This experimental apparatus consists of 30 m 2 of flat-plate solar collectors, a laboratory with 75 m 2 floor area for heating purposes, a latent heat thermal energy storage tank that is filled by 1500 kg of encapsulated phase-change material (PCM), a heat pump with double evaporators (air- and water-sourced) and one condenser, a water circulating pump and other measuring equipment. The experimental results are obtained in December, January, February, March, April and May in the heating season of 1991 for the two heat pump systems used. The experimentally obtained results are used to calculate the collector efficiency, heat pump coefficient of performance (COP), system COP, storage efficiency and total energy consumption of the system during the heating season. The mean values of the collector efficiency, heat pump COP, system COP and storage efficiency were around to be 70, 4.2, 4.0, and 60%, respectively.

Solar-assisted heat pump and energy storage for residential heating

In order to investigate the performance of a solar-assisted heat pump system with energy storage for residential heating in the Black Sea region of Turkey, an experimental setup was constructed. This experimental apparatus consisted of flat plate solar collectors with total area of 30 m 2, a laboratory building with 75 m 2 floor area for heating purpose, a latent heat thermal energy storage tank filled by 1500 kg encapsulated phase change material (PCM), a heat pump with double evaporators (air-sourced and watersourced) and one condenser, a water circulating pump, and measuring equipments. The experimental results were obtained December-May during the heating season of 1992 for the solar-assisted heat pump system used. The experimentally obtained results were used to calculate the collector efficiency, coefficient of performance of heat pump (COP), system COP, storage efficiency, and total energy consumption of the system during the heating season. The mean value of the collector efficiency, heat pump COP, system COP, and storage efficiency were found 70%, 4.5%, 4.0%, and 60%, respectively.

Cost benefit of a cooling energy storage system

Since the air conditioner (A/C) load contributes 30% of the peak demand of Taiwan Power Company (Taipower) system during the summer season, load management by A/C load clipping has become one of the most important topics in the Taipower system. Since the eutectic salt is a complete inorganic compound with a freezing point of 47 degrees F and latent heat of 41 Btu/lb, it is a good medium for an energy storage system. An A/C system with an 1800 RT-HR eutectic salt energy storage tank was built on the campus of the National Sun Yat-Sen University (NSYSU) for demonstrating the cooling energy storage (CES) system. By computer simulation, it is found that 41.1% of the electric peak demand has been reduced and 56% of the energy consumption has been shifted from peak hours to off-peak hours by the CES-system. In this paper, the mathematical model of the eutectic salt CES-system has been developed for computer simulation of the energy storage system. It is found that the optimal capacity of the storage tank is determined by the off-peak time period and the largest annual electricity charge saving could be obtained by applying the smallest nominal chiller size under the optimal operating conditions. >

Experimental investigation of the exergetic efficiency of solar assisted and energy storage heat pump systems

In order to investigate the effects of new developments of thermal energy storage techniques on the exergetic efficiency of a solar assisted heat pump system with a thermal storage tank, an experimental set up was constructed. This experimental apparatus consists of 18 solar collectors, a latent heat thermal energy storage tank (containing phase change storage material), a heat exchanger, a heat pump with double evaporators and a circulating pump. Experimental results are obtained for typical days during each month of June, July and August for Trabzon (41°N) in this period of the research programme. The exergetic efficiencies are calculated using the experimental data and comparisons are performed among the different systems.

Solar-assisted heat pump systems and energy storage

An experimental solar-assisted heat pump system with solar energy storage in encapsulated phase change material (PCM) packings at the Karadeniz Technical University in Trabzon, Turkey is described. It includes 30 m 2 solar collectors, a latent-heat thermal energy storage tank filled with PCM, a heat exchanger, a heat pump with double evaporators and condenser, and a conventional air conditioning channel. We have analyzed the system's behavior from July to August, 1990. The data processed has shown that each of the systems has apparently performed adequately. Collector efficiency is 0.80, heat pump coefficient of performance range is around 7, and the storage efficiency reaches 0.60. When the investigations are accomplished, we will publish the experimental results in detail.

Studies of Radiative Cooling Systems for Storing Thermal Energy

The thermal performance of an uncovered radiator and a radiative cooling system was investigated experimentally and theoretically. The net radiative power of a black painted surface at ambient air temperature was measured by heat flux plates at night in order to use the results for predicting temperatures of the radiator surface and the fluid in the cooling system on the same night. The net radiative power obtained by the measurements was 40–60 W/m2 on clear nights in the summer and 60–80 W/m2 in the fall and winter. The average temperature of the energy storage tank on clear nights became 2–5°C below the ambient temperature. The experimental and analytical results agreed well with each other.

Studies of a radiative cooling system for storing thermal energy by forced circulation.

The net radiative power of a black-pained surface at an ambient temperature of the ambient was measured at night, and the result was used to predict the temperature distributions of a radiative cooling system, which consisted of a pump, a thermal energy storage tank of 66.7 liters in the volume, and two radiator plates, each of which effective length was 1.92 m and width was 0.93 m. The net radiative power obtained on a clear night was about 4060 W/m2 in the summer and 6080 W/m2 in the fall and winter. The average temperature of the thermal energy storage became about 2°C below the ambient in the fall and 5°C below in the winter. The analytical results of the temperature distributions of the radiator and the water in the storage tank agreed well with the experimental results.

Thermal Performance of Submerged Coil Heat Exchangers Used in Solar Energy Storage Tanks

It can be seen from the test results that for the coil flow rate range of interest in solar DHW systems submersed coil heat exchangers can have effectiveness values as low as 0.3 for double-wall coils. This translates into a penalty of 12 to 15 percent for system performance. Inlet and outlet temperatures for the coil are easily measured. The average tank fluid temperature can be determined by inserting a thermocouple rod into the tank along the centerline. The effectiveness of submersed coils is a function of both flow rate and temperature differential between T /SUB coil/ /SUB in/ and T /SUB tank/ . For the purposes of system performance calculations, using programs such as FCHART and SOLCOST which require a single value of epsilon as input, an average value of epsilon can be chosen, representative of the coil flow rate and an intermediate value of temperature differential. This approximation introduces negligible error into the system performance results due to the relative insensitivity of the heat exchanger penalty factor, F' /SUB R/ /F /SUB R/ , with variations in epsilon for epsilon values above 0.5.

Plastic screens being tested

Polyurethane fibers were fabricated using an electrospinning method with aluminum hydroxide and multi-walled carbon nanotubes (MWCNTs) as flame-retardant additives to improve the thermal oxidation stability of the polyurethane fibers. The MWCNTs were incorporated into the polyurethane fibers after oxyfluorination treatment to improve the dispersivity and compatability. The thermal properties and anti-oxidation stabilities of these polyurethane fibers were investigated under nitrogen and oxygen flows from room temperature to 600 °C to determine the effects of the MWCNTs and aluminum hydroxide additives. The aluminum hydroxide acted as an energy storage tank by releasing water, resulting in an endothermic reaction. The MWCNTs promoted the formation of a charred layer that acted as a protective film to prevent the decomposition of the polyurethane by oxygen radicals. The flame-retardant properties were also improved by an enhanced gel-type structural network generated by the MWCNTs. The integral procedure decomposition temperature and activation energy increased significantly, indicating that the flame-retardant properties of the polyurethane fibers improved. These results are attributed to the aluminum hydroxide, MWCNT additives, and the oxyfluorination treatment.