Cool Storage System Research Articles

Numerical study on ground source heat pump integrated with phase change material cooling storage system in office building

Ground source heat pump (GSHP) integrated with phase change material (PCM) cooling storage system could shift peak load and save electricity charge. This paper studied the optimal control method of GSHP system integrated with PCM cooling storage tank in an office building in Wuhan, China. The energy performance and economic analysis of this combined system under different cooling storage ratios (the ratio of PCM cooling storage tank capacity to total system cooling capacity) were analyzed. The optimal operation mode and optimal cooling storage ratio were obtained for this combined system. Considering initial investment and operation cost, the optimal cooling storage ratio was 40% by numerical study. The annual cost of the GSHP combined PCM cooling storage system under cooling storage ratio of 40% was reduced by 34.2% compared with common GSHP hybrid cooling tower (CT) system.

Hybrid Cooling System for HVDC Convertor Valves

High Voltage Direct Current Transmission (HVDC), known as a future energy "highway", plays a key role in the history of electric power system development. In this paper, the present status and future prospect of HVDC convertor valves cooling system in china is analyzed. The performance of HVDC convertor valve cooling system is affected by dry, high temperature, cool weather and sand. Air cooling system is referred to be the most suitable outside cooling system of convertor valve in water scarce areas due to its many advantages such as the antifreezing ability, sand prevention and zero emission of sewage. A hybrid cooling system for cool storage system combined with air cooling system was presented. The experimental result shows this system can be used in desert area like Hami area etc.

Exergy analysis of a gas-hydrate cool storage system

Based on exergy analysis of charging and discharging processes in a gas-hydrate cool storage system, the formulas for exergy efficiency at the sensible heat transfer stage and the phase change stage corresponding to gas-hydrate charging and discharging processes are obtained. Furthermore, the overall exergy efficiency expressions of charging, discharging processes and the thermodynamic cycle of the gas-hydrate cool storage system are obtained. By using the above expressions, the effects of number of transfer units, the inlet temperatures of the cooling medium and the heating medium on exergy efficiencies of the gas-hydrate cool storage system are emphatically analyzed. The research results can be directly used to evaluate the performance of gas-hydrate cool storage systems and design more efficient energy systems by reducing the sources of inefficiency in gas-hydrate cool storage systems.

Feasibility study of domestic cooling storage balls to reduce the energy cost of central air conditioning system

Although cooling storage system used broadly in the world, it is rarely applied in Viet Nam due to their high import expense that increase the initial cost. For that reason, in this article, we study on theories, and experiments about cooling storage sphere with expect to create the base for populising it in our country. That will contribute the efficiency of energy using to our country.

Simulation and experimental validation of soil cool storage with seasonal natural energy

For the purpose of reducing energy consumption by summer air conditioning and utilizing renewable resources, this paper presents a new type of soil cool storage system with seasonal natural cold source In the cool storage system, the natural cool energy is stored in soil by ground heat exchanger during the cold season and is extracted for space cooling in the summer. Based on film moisture migration theory, a moisture-heat transfer coupling mathematical model is brought up to describe the charging and discharging processes of freeze-thaw phase change of the soil. Besides, a new method is presented that variable time step size is used to solve nonlinear phase change problems numerically. Moreover, a comparison of the model predictions and experimental data shows that the model has good prediction accuracy. The parametric studies indicate that the soil cool storage system full meets the air conditioning needs and has excellence in economic performance. The research results prove that the feasibility of inter-seasonal cool storage system using shallow soil in severe cold regions.

Numerical Investigation of a PCM Heat Exchanger for Latent Cool Storage

Latent cool storage system for air conditioning is largely used in coolness systems. This system includes phase change materials (PCMs) contained in plate type capsules. Solidification of PCMs inside these capsules has been formulated by using a conduction model. An enthalpy method with finite control volume approach is used. This model has been validated by comparison with available experimental results of the literature. The model is then used for numerical study on ice banks of the parallel plate type. The temperature and enthalpy history, the heat flow rate and the evolution of the solidified mass fraction are presented and discussed. In the extreme conditions, complete loading of the cool storage tank is achieved within 3h 37 mn. 81% of loaded energy is done in 57% of the total solidification time.

Thermal performance of a multiple PCM thermal storage unit for free cooling

As demand for refrigeration and air conditioning increased during the last decade, the opportunities have expanded for using thermal energy storage (TES) systems in an economically advantageous manner in place of conventional cooling plants. Many cool storage systems use phase change materials (PCMs) and achieve peak load shifting in buildings. This work presents numerical investigations of the performance enhancement of a free cooling system using a TES unit employing multiple PCMs. The TES unit is composed of a number of rectangular channels for the flowing heat transfer fluid, separated by PCM slabs. Using the effective heat capacity method, the melting and solidification of the PCM is solved. The forced convective heat transfer inside the channels is analyzed by solving the energy equation, which is coupled with the heat conduction equation in the container wall. The effect of design parameters such as PCM slab length, thickness and fluid passage gap on the storage performance is also investigated using an energy based optimization. The results show that a system which can guarantee comfort conditions for the climate of Tabriz, Iran has an optimum COP of 7.0. This could be achieved by a combination of CaCl2·6H2O with RT25 with the optimum air channel thickness of 3.2mm, length of 1.3m and PCM slab thickness of 10mm.

Experimental study on thermophysical properties of nanofluids as phase-change material (PCM) in low temperature cool storage

In this article, a new sort of nanofluid phase change materials (PCMs) is developed by suspending a small amount of TiO2 nanoparticles in saturated BaCl2 aqueous solution. Its thermal conductivities, supercooling degree, latent heat, specific heat, and rheological behaviors of the nanofluids PCMs were investigated. The experimental results show that with volume fraction is 1.130%, the thermal conductivities of nanofluids PCMs is enhanced by 12.76% at −5°C, the supercooling degree is reduced by 84.92%. The latent heat and specific heat are slightly decreased with suspending nanoparticles. The viscosity increased with the increasing volume fraction, which will have no effect on the cool storage system. The higher thermal performances of nanofluids PCMs indicate that they are suitable for the industries low temperature energy storage.

A Multistage Cool Storage System of Natural Coldness Resource Based on Heat Pipe

This article proposes a multistage cool storage system of natural coldness resource storage joint operation with refrigeration unit cool storage using heat pipe as heat transfer components. This system can realize both cold energy stored in winter used in summer which is called “Seasonal storage of cold energy” and cold energy stored at night used in the day which is called “cool storage day by day”. When the user needs cooling, it will choose different cycle way to release cold energy to the cooling user according to the temperature grade of the cool storage medium and the cooling load of the user. This system can achieve the purpose of energy conservation and environment protection.

Solidification Characteristics Modeling of Phase Change Material in Plate Capsule of Cool Storage System

The analytical solutions to solidification characteristics of a phase change material in the plate capsule of a cool storage system are presented. The influence of the Stefan number (the ratio of sensible heat to latent heat of a cool storage material) on phase change solidification thickness and temperature distribution in the solid region is analyzed. The phase change solidification thickness and temperature distribution in the solid region with second-order accuracy solutions are compared with those with first-order accuracy solutions for different Stefan numbers. It is found that the difference in temperature distribution in the solid region between second-order accuracy solutions and first-order accuracy solutions is very small as the Stefan number is small (i.e., Ste ≤ 0.1). In addition, the results present that the difference in phase change solidification thickness between second-order accuracy solutions and first-order accuracy solutions is small as the Stefan number is small (i.e., Ste ≤ 0.1). The phase change solidification thickness can be calculated using second-order accuracy solutions to obtain accurate calculation results as the Stefan number is large (i.e., Ste ≥ 0.1).

Thermodynamic optimization for crystallization process of gas hydrate

Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL SUMMARY In this paper, thermodynamic optimization is applied to analyze the crystallization process of the gas hydrate related to the gas hydrate cool storage system. Thermodynamic optimization model of the gas hydrate crystallization process is established. By taking the entropy generation minimization as the optimization objective, both the optimal control strategy and the optimal cooling rate of the gas hydrate crystallization process are determined. The minimum entropy generation corresponding to the optimal cooling rate decreases by 7.8% compared with normal situation. The results presented in this paper can provide important guidelines for optimal design and operation of the gas hydrate crystallization process. Copyright © 2010 John Wiley & Sons, Ltd. Citing Literature Volume36, Issue2February 2012Pages 269-276 RelatedInformation

Entropy generation minimization for charging and discharging processes in a gas-hydrate cool storage system

Thermodynamic optimization models of gas-hydrate cool storage and cool release processes are established in this paper. The optimal temperature configuration at the sensible heat transfer stage and the optimal gas hydrate phase change rate configuration at the phase change stage in the processes of gas hydrate charging and discharging are obtained by taking entropy generation minimization as optimization objective. The optimal control strategies of the cool storage system are determined. The research results indicate that the optimal operating characteristic of the gas-hydrate cool storage system can be achieved by keeping the phase change rates uniform, which are regulated and controlled according to constant heat transfer rates in the charging and discharging processes of gas hydrate. The analysis method and the results presented in this paper can provide important guidelines for optimal design and operation of gas-hydrate cool storage system.

Experimental study on cool release process of gas-hydrate with additives

Cool release process of phase change material (PCM) includes the dissolution process of the PCM. Experimental research on the cool release process in a new gas-hydrate cool storage system is performed in this paper. In the system, the inner-heat exchange/outer-crystallization technology and the integrated condenser/evaporator structure design were adopted. The influences of different proportions of calcium hypochlorite or benzenesulfonic acid sodium salt on the dissolution process are studied. The results show that the instantaneous dissolution rate is close to twice as the corresponding instantaneous formation rate of gas-hydrate, and the cold energy release rate, i.e. energy release per unit time, is obviously higher than the corresponding cold energy storage rate at different conditions, which is mainly due to the heat transfer temperature difference of the discharging (release) and charging (store) processes. Both the charging and the discharging processes are simultaneously dominated by the heat transfer and the mass transfer processes. However, as to the dissolution (discharging) process of the gas-hydrate by heating, the effect of the heat transfer process is the main influence factor. The temperature difference between the heating medium and the gas-hydrate in the discharging process, which is larger than that between the cooling medium and the gas-hydrate in the charging process, makes a higher cold energy release rate compared with the cold energy storage rate. The results also indicate that the dissolution rate of gas-hydrate is accelerated, and the cold energy release rate of the cool storage system is increased by adding reasonable proportions of the additives.

Using the fuzzy multi-criteria model to select the optimal cool storage system for air conditioning

Four existing cool storage systems for air conditioning, chilled water storage, ice storage, phase change material cool storage and high temperature water cool storage, are evaluated and compared in multi-criteria. Due to the availability and uncertainty of qualitative criteria, this paper presents a fuzzy multi-criteria model to select the optimal cool storage system. In the evaluation process, the optimal weighting method combines the subjectivity of decision-maker and the objectivity of numerical data to obtain the comprehensive weights of criteria and avoids the subjective one-sidedness of weights. The fuzzy multi-criteria model applied to select the best cool storage system in detail demonstrates the evaluation process and its applicability in selecting an optimal system. The evaluation results indicate that ratio of cooling density and ratio of cooling capacity are the most important factors in cool storage systems, and ice cool storage system is the optimal option.

A Near-Optimal Control Strategy for Cool Storage Systems with Dynamic Electric Rates (RP-1252)

A near-optimal control method was developed for charging and discharging of cool storage systems when real-time pricing (RTP) electric rates are available The algorithm requires relatively low-cost measurements (cooling load and storage state of charge), requires very little plantspecific information, is computationally simple, and ensures that building cooling requirements are always met (e.g., storage isn't prematurely depleted). The control method was evaluated for ice storage systems using a simulation tool for different combinations of cooling plants, storage sizes, buildings, locations, and RTP rates. The simplified method worked well in all cases and gave annual costs within approximately 2% of the minimum possible costs associated with optimal control.

Air Conditioning: Selecting the Optimal Cool Storage System

The present paper introduces the notion of cool storage system and summarizes its benefits, especially the environmental ones: Air emissions savings and CFC reductions. Four existing cool storage types are outlined: chilled water storage, ice storage, PCM (phase change material) cool storage and high temperature water cool storage and a commonly employed value analysis method is introduced and applied to select the best cool storage option. An evaluating method is established and the best type of cool storage is obtained. The results indicate that high temperature water cool storage is the optimal option, and the method of value analysis has applicability in selecting an optimal system.

Air Conditioning: Selecting the Optimal Cool Storage System

The present paper introduces the notion of cool storage system and summarizes its benefits, especially the environmental ones: air emissions savings and CFC reductions. Four existing cool storage types are outlined: chilled water storage, ice storage, PCM (phase change material) cool storage and high temperature water cool storage and a commonly employed value analysis method is introduced and applied to select the best cool storage option. An evaluating method is established and the best type of cool storage is obtained. The results indicate that high temperature water cool storage is the optimal option, and the method of value analysis has applicability in selecting an optimal system.

Influences of additives on the gas hydrate cool storage process in a new gas hydrate cool storage system

Abstract Experimental research on the crystallization process of the gas hydrate HCFC141b is performed for this paper. The influences of different proportions of calcium hypochlorite or benzenesulfonic acid sodium salt on the crystallization process are studied. The results show that the degree of subcooling of formation is obviously decreased, and the formation rate of the gas hydrate is greatly accelerated by adding reasonable proportions of the additives. The degree of subcooling of formation decreases 0.78 °C by adding benzenesulfonic acid sodium salt of 0.03%, and the formation rate of the gas hydrate increases 0.2 g/s by adding calcium hypochlorite of 0.08%. In the cool storage system, clathrate hydrates can be formed effectively, and thermal energy can be stored efficiently. When adding benzenesulfonic acid sodium salt of 0.03%, the cold energy stored is 4.74 MJ, and the cool storage density is 206.07 MJ/m3. The performance of this cool storage system can meet the needs of practical air conditioning engineering.

06/01278 A continuous/discrete simulation of controlled atmosphere (CA) cool storage systems: validation using industrial CA cool storage: Nahor, H. B. et al. International Journal of Refrigeration, 2005, 28, (4), 461–470

06/01278 A continuous/discrete simulation of controlled atmosphere (CA) cool storage systems: validation using industrial CA cool storage: Nahor, H. B. et al. International Journal of Refrigeration, 2005, 28, (4), 461–470

06/01277 A continuous/discrete simulation of controlled atmosphere (CA) cool storage systems: evaluation of plant performance/design and product quality evolution: Nahor, H. B. et al. International Journal of Refrigeration, 2005, 28, (4), 471–480

06/01277 A continuous/discrete simulation of controlled atmosphere (CA) cool storage systems: evaluation of plant performance/design and product quality evolution: Nahor, H. B. et al. International Journal of Refrigeration, 2005, 28, (4), 471–480