Ice Storage Tank Research Articles

Performance evaluation of ultrasonic-assisted dynamic ice melting in ice storage systems: An experimental study

This study presents the construction of an ice storage tank equipped with an internal ice-on-coil system. The cooling performance of the ice storage system is enhanced by utilizing the cavitation phenomenon induced by ultrasonic vibration in water. Active water circulation and spraying within the tank enhance cooling efficiency by promoting uniform temperature distribution. An analysis is conducted on the impact of various operating parameters, such as output powers of 200 W, 400 W, and 584 W, frequencies of 40 kHz, 80 kHz, and 120 kHz, and three different placements of the oscillator, on the cooling performance of ultrasonic-assisted static ice melting, dynamic ice melting, and ultrasonic-assisted dynamic ice melting systems. Ultrasonic-assisted static ice melting refers to ice melting with stationary water, while ultrasonic-assisted dynamic ice melting involves water circulation, enhancing heat transfer. The study examines performance indicators like instantaneous cooling rate, cumulative cooling capacity, average cooling rate, melting time, and heat gain by the system. The findings indicate that higher ultrasonic power levels enhance the average cooling rate and reduce the melting time by approximately 50 % and 32.2 %, respectively. However, the frequency does not have a significant effect on the cooling performance. In addition, the ice storage system had a significant increase in cooling rate of 294.87 % when utilizing the ultrasonic-assisted dynamic ice melting system. Furthermore, the melting time was lowered by 71 % in comparison to the static ice melting method. Of all the parameters, the power parameter has the greatest impact. The impact of the ultrasonic oscillator placement parameter is secondary, while the influence of the frequency parameter on the cooling performance is not significant.

Experimental study on the influence of gas-blowing flow rate on the cold discharge characteristics of external ice-melting ice storage system

External ice-melting ice storage system has the advantage of fast cold discharge. However, the instability of outlet water temperature limits its practical application. In this paper, an experimental bench is built for testing cold discharge performance of the external ice-melting ice storage system combined with a gas-blowing device based on theoretical analysis. The influence of different gas-blowing flow rates on the vertical temperature distribution inside the ice storage tank, outlet water temperature, cold discharge rate, instantaneous cold discharge capacity, and total cold discharge capacity is analyzed and compared during the cold discharge process by experiments. The experimental results show that as the gas-blowing flow rate increases, the convective heat transfer between the water and ice in the water space of the ice storage tank is enhanced, the outlet water temperature decreases, and the cold discharge rate increases. Through comprehensive analysis, it is found that for a small external ice-melting ice storage system in this experiment, the outstanding comprehensive performance can be achieved with 1L/min gas-blowing flow rate, which. The average outlet water temperature during the latent heat phase is 1.9 °C lower and the cold discharge rate is 34.8 % higher than that without gas blowing.

Case study of variable speed photovoltaic direct-driven ice-storage air conditioning system in Wuhu

In order to meet the contradiction between the growing demand for refrigeration and energy scarcity, this paper proposes a novel photovoltaic ice storage air conditioning system. The system is directly driven by a photovoltaic array. The performance of the system was studied through experiments, and a mathematical model was constructed for comparative verification. The experimental results show that the daytime cooling COP of the system is 1.18, the photovoltaic conversion efficiency is 6.29 %, and the nighttime cooling time is 9 h, which basically meets the cooling needs. Through simulation, the performance of the system was optimized, and the results showed that an increase in the initial water volume and temperature of the ice storage tank would increase the cooling COP; the spacing between evaporator pipes increased from 45 mm to 60 mm, resulting in a 7.11% increase in COP; the optimal spacing between evaporator fins is 9 mm, which improves performance by 9.11 %.

Increase the integration of renewable energy using flexibility of source-network-load-storage in district cooling system

The flexibility of power systems is critical to cope with the variability and uncertainty caused by the integration of renewable energy resources. Incorporating district cooling systems (DCSs) into power systems is an emerging approach to provide flexibility for renewable energy utilization. However, the existing models of DCS components, such as ice-storage cooling sources, cooling pipelines, and cold warehouses, are simplified, failing to fully utilize that flexibility, which brings difficulties for renewable energy utilization. Therefore, this paper proposed a coordinated operational strategy for an integrated power and cooling system combining detailed operating characteristics of DCSs to exploit the potential flexibility of DCSs for better integration of renewable energy. The primary cooling source components, including the chiller, ice storage tank, pump, and cooling tower, are established to model a detailed process of cooling generation and storage. The thermal inertial of district cooling networks (DCNs) is formulated as a quasi-dynamic model by considering dynamical temperature characteristics and transmission delay to exploit the virtual energy storage capacity of the cooling water pipeline. Moreover, the thermal inertia of the demand side, such as buildings and cold warehouses, is considered to utilize thermal storage capacity. The objective function of the proposed optimization model is to minimize the overall operating cost of the integrated power and cooling system. Numerical simulations show that the proposed method could reduce the operating cost by 15.4% and the wind curtailment rate by 86.2%, indicating better performance of the proposed method in improving economic benefits and reducing renewable energy curtailment.

Numerical simulation of convective heat transfer in the discharging process of external ice-melting ice storage systems

The external ice-melting ice storage system was widely used because of its advantages of reducing peak power consumption, reducing energy consumption and emissions, and fast ice melting speed. However, designing the external ice-melting ice storage system proved to be a challenge, and the structure and flow of the water distribution system needed to be fully considered. In particular, the problem of unstable outlet water temperature limited the practical application of the external melting ice storage system. Aiming at the problem of unstable outlet water temperature, a three-dimensional CFD phase change model was constructed in this paper. By comparing with the experimental data, the impact of varying water flow rates on the thermal and cooling properties of the was investigated. The results indicated that when the water flow rate was 226 ml/min for the system with an ice thickness of 74 mm, the outlet temperature of the ice storage tank was consistently below 5°C, the Nusselt number of ice and water remained constant, and the convective heat transfer effect was improved. The numerical simulation results provided guidance for the design and practical application of the water distribution system of the external melting ice storage system.

Experimental study of dynamic melting process in an ice-on-coil storage system

Ice storage air conditioners in the field of refrigeration and air conditioning have the ability to effectively regulate the power load curve by mitigating the occurrence of high peaks and filling in the low troughs in power consumption. In order to enhance the applicability of the ice-storage air conditioner, a method of experimental analysis was utilized to incorporate a dynamic circulation system into the specially designed ice-melting ice storage tank. The system consists predominantly of circulation pumps, transportation tubes, and sprinkler nozzles. The study examined the effects of several parameters, including the arrangement of sprinkler nozzles, the flow rate of the sprinkler nozzles, the temperature of the brine at the inlet, and the flow rate of the brine, on the performance of the system. The assessment of the performance was conducted by considering the average discharge rate, total discharge capacity, duration of melting, discharge rate, and the distribution of temperature within the phase change material (PCM) tank. Based on the empirical findings, the dynamic ice melting system exhibited a notable increase in the average discharge rate, ranging from 60.7 % to 89.2 %, as compared to the static ice melting system. The duration of ice melting experienced a decrease ranging from 45.3 % to 54.3 %, while the distribution of temperature in the tank containing PCM exhibited a greater level of uniformity in comparison to the process of static ice melting. The staggered arrangement of nozzles has demonstrated superior effectiveness in terms of parameter impacts. The study revealed a positive correlation between the rate at which ice melts and the flow rate of the sprinkler, the temperature at which brine enters the system, and the rate at which brine flows.

Performance analysis of ice storage tank with smooth-tube and corrugated-tube heat exchangers based on numerical simulation

The ice storage system is of great value to improve the flexibility of building cooling load. In this paper, the two-dimensional physical models of smooth-tube and corrugated-tube heat exchangers ice-storage tank is established with consideration of natural convection. The ice storage process of tubes is numerically simulated using Computational Fluid Dynamics (CFD). The effects of structural parameters on the ice storage performance are comprehensively analyzed, including the pitch and height of corrugation. The results indicate that the ice storage duration of the corrugated-tube heat exchanger is shortened by 7.1% compared with that of the traditional smooth-tube heat exchanger, which is due to the fact that corrugations disrupt the development of the boundary layer and strengthen the fluid mixing. There is the thicker ice layer outside the corrugated tube in comparison with the smooth tube at the same time. In addition, the influence of the corrugated tube structure on its ice storage performance is studied by varying the corrugation pitch and height. If the corrugation pitch is decreased by 41.7% and the corrugation height is increased by 28%, the heat transfer performance of corrugated tubes is improved by 10.3% and 29.4%, respectively.

A novel hybrid ice storage design applicable for commercial showcase with refrigerator and freezer

In this research, a novel hybrid design of ice storage system is proposed in a showcase with refrigerators and freezers. The design concept and performance of the hybrid ice storage system are demonstrated and analyzed in detail. The cold energy is stored in the ice storage tank during off-peak hours, and the cold energy is released during peak hours. This study uses the combination of internal and external melting to supply the cold energy in the ice storage tank, and to the refrigerator and freezer at the same time. It is found that the ice storage system can employ ice melting to reduce the condensation temperature during peak hours, which can effectively improve the coefficient of performance of the refrigerator system (COP). The COP of the freezer and refrigerator system is approximately 2.053 and 2.579 for the refrigerated mode and they were further improved to 2.806 and 4.449 respectively in ice melting mode. The experimental results show that the ice storage system in this research consumes more energy than the general system. However, the design can have 10 % electricity expenditure saving. During the peak period, 22 % of the electricity consumption can be transferred to the off-peak electricity consumption. Yet, the ice storage system can be successfully applied in refrigerator and freezer cabinets with the loading temperatures of 4–7 °C for refrigerator and − 12 to −9 °C for freezer. Note that none of the existing studies were reported with the ice storage systems that are capable of demonstrating cold storage below 0 °C.

Comparison study on three ice storage equipments using micro-tube heat exchanger for cold chain logistics

ABSTRACT Freezing efficiency was the main factor affecting the efficiency of cold chain logistics and transportation. To further the ice storage performance, three mathematical models of the ice storage equipments were established to explore the influence of the number and the diameter of the tubes on the freezing time, heat flux, and natural convection by analyzing the distribution of the ice fraction and velocity. The results showed that the total freezing time of Type II and Type III, which were arranged the micro-tube, were 76.42 min and 137.50 min, which was more than 90% less than that of type I. Due to a ring cavity of water appearing near the shell of the ice storage tank increased the water natural convection, the freezing time required to increase the ice fraction by 0.05 gradually increased especially with the ice fraction greater than 0.95. To better evaluate the ice storage performance, the freezing efficiency was introduced. The freezing efficiency of Type II and Type III was lower than that of Type I by more than 2.24% and 2.14%, respectively, for the ice fraction range of 0.75 ~ 1. Given the freezing time and ice storage efficiency, it could be found that using type II and making the ice storage rate reach 0.95 could shorten the freezing time and improve the ice storage efficiency.

Reduce operational costs of thermal power units in power systems using the flexibility of district cooling systems

The high volatility of wind generation causes the thermal power units to start up and shut down frequently because there is a lack of flexibility in the power systems, which poses a challenge to economic operation. With the increase in cooling demand, district cooling systems (DCSs) have received attention in recent years and have been built in many regions, which offer a novel option to alleviate the above problems by utilizing the complementarity between power and cooling systems. In a typical DCS, the cooling source is a key component that generates cooling energy for the entire cooling system. Utilization of the cooling storage capacity of cooling sources in DCSs is an economical and efficient measure for more operational flexibility of power systems. Therefore, this paper proposes a unit commitment model with combined power systems and DCSs to reduce the operational costs of thermal power units and wind curtailment. In this model, an accurate model of a cooling source with an ice storage tank, where the cooling characteristics and energy transmission process are reflected, is built to fully excavate the flexibility potential of DCSs. Finally, numerical simulations are performed to show that the proposed method reduces the operational costs by 15.78% within a scheduling day and makes the wind curtailment close to zero. The results of the above comparison demonstrate that the method can improve the operational economy and encourage wind power integration while assuring an adequate supply of electricity and cooling.

The Optimal Daily Dispatch of Ice-Storage Air-Conditioning Systems

In this paper, the Ant-based Radial Basis Function Network (ARBFN) is proposed to determine the optimal daily dispatch of ice-storage air-conditioning systems. ARBFN is a novel algorithm that is integrated into the Ant Colony Optimization and Radial Basis Function Network. ARBFN is used to construct the function of the cost and operation for each chiller and ice-storage tank and is used to simulate the polynomial function of the cooling load and the cost of power consumption. The best learning rate in the training process is adjusted in ARBFN to improve the accuracy of constructing models for chillers and ice-storage tanks. The electricity savings are thus 4.130% on a summer day and 7.381% on a non-summer day. The results have shown that ARBFN can more accurately calculate the actual power consumption and cooling capability of each chiller and ice-storage tank. Lastly, ACO is used to calculate the daily dispatch of the ice-storage air-conditioning system. The results demonstrated the optimization of energy savings and efficiency for the operation of the ice-storage air-conditioning system.

Solidification analysis in an ice-on-coil ice storage system: Experimental and numerical approaches

Rapid economic growth has led to energy resources shortages, creating unique challenges for developing countries whose activities depend on energy. Thermal energy storage is an important field of technology that can be deployed as a reliable method to decrease net energy usage. For example, ice storage systems are one of the most efficient methods for saving cold energy. In this work, a combined experimental and numerical study has been carried out on the freezing process or solidification as charge mode in a novel ice-on-coil cold storage system with coil tube. Initial experimental results show that the initially designed evaporator, horizontal shell and coil tube heat exchanger (used to transfer cold energy between a mixture of water/ethylene glycol and refrigerant) failed to form uniform ice on the outer surface of the coil tube inside the ice tank. Also, the thickness of ice decreases from the top to the bottom of the coil, while trying to create a uniform thickness of ice around the coil is one of the main challenges in improving the performance of the proposed cold storage system. In the second part of this work, baffles are inserted inside the evaporator to create transverse fluid flows and to prevent shortcut flow, which leads to better heat transfer rates and, consequently, more uniform ice production around the coil tube. The results depict that although baffle placement demonstrates a slightly positive impact on improving the ice thickness along the coil, overall, it fails to eliminate the non-uniformity of ice production along the entire length of the coil tube. In the third section, a modified evaporator with four connected horizontal-placed coils is employed. According to the obtained results, it can be concluded that after 180 min, by employing the modified evaporator, ice thickness has increased by 14.71, 13.51, and 3.39 % in the bottom, middle, and top of the coil, respectively. It can be seen that utilizing the modified version of evaporator with four horizontal-placed coils leads to enhancement in the ice thickness specially at the bottom of the coil where the ice thickness is less than for the rest of the examined points, which was considered as one of the weaknesses of the primary system. Finally, in the last section, to realize better the solidification process around the coil tube inside the ice storage tank, the ice production process is modeled by performing three-dimensional simulations based on the finite volume method. The proposed model is then validated by using the experimental results.

Evaluating the dynamic behaviour of wind-powered compression refrigeration cycle integrated with an ice storage tank for air conditioning application

Looking for an alternative renewable energy source to meet the energy demand of refrigeration and air conditioning systems has been a matter of high priority. The current study proposes a wind-powered compression refrigeration cycle integrated with an ice storage tank in order to meet the cooling demand of a building. An educational building in Zabol, a city in the southeast of Iran, is selected as a case study. A comprehensive model based on energy and exergy analyses is carried out for all components to investigate their performance. The effects of design parameters are evaluated through the parametric study. The results show that the refrigeration production has less dependency to the evaporator temperature compared the other parameters such as wind speed. A dynamic behaviour study indicates that the proposed system daily coefficient of performance has grown 17 % compared to the conventional cycle. Also, in the maximum required cooling demand hour, COP has ascended significantly. The maximum storage refrigeration inside the ice tank is about 46 % of total refrigeration production occurring at 4 AM, while the maximum consumption of stored refrigeration from the ice tank is about 87 %, happening at 4 PM. At the end of the design day, 5 % of tank fluid mass remains in the solid state. The 48 % of total energy passing through the system in work and heat shapes from various equipment destroyed via exergy destruction. The wind turbine (27.8 % of total weight) and the ice storage tank (23.14 % of total weight) have the maximum exergy destruction, respectively.

Flow Characteristics and Heat-Transfer Enhancement of Air Agitation in Ice Storage Air Conditioning Systems

A large number of bubbles generated by the air agitation device in an external melting ice storage system can cause the disturbance of the ice–water mixture, which can enhance the heat transfer and contribute to the reduction in energy consumption. The structural design and optimization of the air agitation device in an external melting ice storage system is the key issue for energy savings. In this study, the influence of different orifice spacings and diameters on the distribution of the gas–liquid flow field, gas holdup, heat-transfer coefficient, and power consumption in the ice storage tank was investigated by numerical simulation. The simulated results showed that the heat-transfer coefficient of the ice–water mixture with air bubbles should be 3–5 times higher than the natural convection when the air superficial velocity is 0.03 m/s. The gas holdup was mainly affected by the orifice spacing, and the maximum varied from 5.0% to 8.2%. When the orifice spacing was less than 150 mm, the gas holdup changed a little in the horizontal direction, and the uniformity became worse when the orifice spacing was larger than 180 mm. An orifice diameter larger than 3 mm can improve the heat transfer and cause less air-compressing energy consumption, which decreased by approximately 1.62%.

Heating performance of a novel solar–air complementary building energy system with an energy storage feature

To compensate for the defects of the air source heat pump at low temperatures, we propose a novel solar–air complementary energy system for buildings that included an energy storage feature. This system uses heat released by the water solidification process as a low-temperature heat source for the heat pump, while utilizing air as an auxiliary energy source. While the heat storage tank supplies the building during the day, the energy in the ice storage tank is restored by collecting photovoltaic waste heat from photovoltaic photothermal (PV/T) modules or by using air energy to melt stored ice. This study evaluated the heating performance of the system in winter by analyzing storage and release of heat as well as storage and melting of ice. The results show that for heat storage by ice mode, the average coefficient of performance (COP) of the heat pump was 2.60 and that of the proposed system was 2.03. For ice melting by solar mode, the average heat collection efficiency of the PV/T module was 35.3%. An optimization strategy for system operation was provided, and the economy of the system was analyzed. The system exhibited good operational stability and reduced the peak power grid load, thus providing a novel energy supply solution for cold regions.

Ultrasonic wave promoting ice melt in ice storage tank based on polynomial fitting calculation model

Abstract The existence of floating ice in ice storage tanks in an ice storage system affects the normal operation of the ice storage automatic control system. For the ice storage tank in an ice storage system, the ice “problem”, puts forward the way of melting ice in an ultrasonic assisted manner. This paper establishes a polynomial mathematical model of observation data changes over time, by setting a variable’s value used to model the polynomial fitting method. It could be used in the design and operation index model or higher polynomial model fitting process of melting ice. Ultrasonic wave is used to solve the floating ice problem of ice storage tank in the operation of ice storage, and the effects of ultrasonic power density, ice-water ratio, ice size, initial ice amount and other parameters on the characteristics of ice melting are tested and analysed through experiments, which provides an important reference for the practical application of this technology. It is found that the ultrasonic wave can obviously promote and strengthen the melting of ice, and the influence of power, ice–water ratio and ice size conforms to the normal theory and practice law. The greater the power, the smaller the ice–water ratio and the smaller the ice size, the faster the melting speed will be. Due to the multiple effects of technology and economy, the power density has an optimal value, which needs to be optimised according to the actual situation in the application. For large size ice, the promotion effect of high-power ultrasonic on melting ice is more obvious.

Experimental and numerical study of a PV/T direct-driven refrigeration/heating system

A photovoltaic/thermal (PV/T) direct-driven refrigeration/heating system was proposed in this paper. This system had the functions of off-grid refrigeration and hot water supply without using batteries. The solar refrigeration efficiency could also be improved by means of PV cell cooling in PV/T modules and compressor speed controlling. In this paper, performance of this system was investigated by experiments and numerical simulations. The influences of the total capacity of PV cells and water temperature in the ice storage tank were also studied. When the number of PV cells increased, the daily cooling capacity per cell increased first, then decreased. This revealed that the capacities of the compressor and PV cells should be designed to improve the PV utilization efficiency. Total cooling capacity of the system increased with the increase of initial water temperature in the ice storage tank. This revealed that high initial water temperature was benefit for system cooling capacity.

Performance of Commercially Open Refrigerated Showcases with and without Ice Storage—A Case Study

This study examines the applicability of the ice storage systems in the small commercial refrigerated showcases through experimental analysis. R-404A is used as the working fluid and various influence of parameter settings and improvements, are discussed in details. In the ice storage system, the condenser is changed from air-cooling (refrigeration mode) to an immersion type that is placed in an ice storage tank, the corresponding condensing temperature and pressure are reduced appreciably. This increased the efficiency and can effectively reduce the peak power consumption. The reduction of the condensing temperature and pressure increased the coefficient of performance (COP) from 3.6 (refrigeration mode) to 6.35 (melting mode), effectively enhancing the refrigeration efficiency. The results indicated that the ice storage system could effectively increase the coefficient of performance from 3.6 to 6.35 during ice melting when compared to the conventional refrigeration system. It also can shift approximately 35% of the power during peak hours and lower the energy cost by USD$ 17.13 per month.

Experimental and numerical investigation on a novel photovoltaic direct-driven ice storage air-conditioning system

In this paper, a photovoltaic direct-driven ice storage air-conditioning (PDISAC) system is proposed and performance of the system is experimentally and theoretically investigated. The proposed system is a battery or inverter less photovoltaic direct-driven system where the DC compressor is directly connected to the PV array. Through the test, it has been found that the proposed system was able to lower the test room temperature below 298.15 K, while the reference room temperature was 306.15 K. Moreover, the experimental refrigeration efficiency and solar-energy utilization efficiency were reported 1.028 and 7.1% respectively. Then, a mathematical model for the progress of ice making and cold storage is presented and verified by the experimental results. Besides, the factors such as the ambient temperature, the initial water temperature and volume in the ice storage tank, and the thickness of the ice layer surrounding the coil have been studied. The simulation results indicate that the initial heat transfer rate at the condensation side drops by 10.8% and refrigeration efficiency drops by 32.7% with the ambient temperature increasing from 298.15 K to 308.15 K. The increment of initial water temperature and initial water volume will lead to an increase in refrigerating capacity and refrigeration efficiency.

Smoothing of Power Consumption in Air Conditioning Systems with Ice Storage: A Receding-Horizon Optimization Approach

The peak of power load brings great challenges to the safety, stability, and economical operation of the modern power system. Building air conditioning refrigeration is one of the main reasons for the peak load. In this paper, we make use of an ice storage tank to smooth the air conditioning load as far as possible so as to achieve the purpose of peak filling. A mathematical model of quadratic programming is established to characterize the trade-off between the lowest energy storage cost and smoothness via a receding-horizon optimization approach. Numerical examples are given to analyze the relationship between ice storage cost and peak filling effect.