Ice cooling storage project

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charging temperatures of -9.0° C to -3.0° C, below the normal operating range of ... resulting from the pressure drop in the ice storage tanks. However, this ..... R-404A is an almost a zoetrope mixture of HFC refrigerants, with zero ozone layer ...
Benha University Shoubra Faculty of Engineering Power Mechanical Engineering Department

Ice cooling storage project For Air Conditioning Applications

Prepared By: Mohamed Ahmed Attia Bayomie And my team 1- Eslam Abdel-Azeem 2- Eslam Amin Mahmoud 3- Eslam Fatouh Abdel-Razik 4- Mohamed Mohamed Farouk 5- Mohamed Kamal Mokhtar 6- Mohamed Tawfik Abed El-Sadek 7- Ahmed Monier Mohamed 2018

Abstract With rising of energy costs and increasing demand for renewable energy sources, cool storage system becomes an interesting option and is considered a key component for any successful thermal system. Therefore the design and development of cool energy storage system, is of vital importance. This study reports the results of an experimental study concerning the effect of changing inlet brine temperature on charging time of spheres and volume flow rate on charging time of balls and speed of solidification in packed-bed ice thermal energy storage (encapsulated system). We used plastic spheres with 28 mm diameter impressed in a solution of ethylene glycol (35% by volume) + water. And we noticed that by increasing volume flow rate, time of solidification decreases and by decreasing inlet brine temperature, charging time and energy stored in spheres increase.

Contents Content

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Chapter one Introduction 1.1 Cool Thermal Storage Systems Technology

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1.2Types of Cool Thermal Storage

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1.2.1 Ice Thermal Storage Systems

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1.2.2 Types of ice thermal storage systems 1.2.2.1 Ice harvesters 1.2.2.2 Ice slurry 1.2.2.3 Encapsulated ice 1.2.2.4 External melts ice on coil storage system 1.2.2.5 Internal melt ice on coil storage system 1.3 Chilled water storage system

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1.4 Operation strategies of cool thermal storage systems 1.4.1 Full storage 1.4.2 Partial storage systems Chapter two

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Review of previous work 2.1 Theoretical studies

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2.2 Experimental studies 2.2.1 Pure PCM Chapter Three Description of the Test Rig

12 12 16

3.1 Refrigeration cycle 3.2. Ethylene Glycol cycle 3.3 Instrumentations & Control Devices

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3.4 Insulation

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Chapter Four Results and discussion 4.1Effect of inlet coolant temperature and flow rate on balls temperature 4.2Effect of flow rate on solidification speed 4.3Energy stored in spheres 4.4The effect of Other parameters or variables Conclusion Appendix Appendix (A) Appendix( B) References

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Chapter 1 Introduction

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Introduction The main function of thermal storage system is to remove or add heat from or to a storage medium to be used at another time. The cool thermal enegy storage (CTES) plays a vital role in central air – conditioning in the large buildings,high powered electronic cooling applications , and various industrial process cooling applications where the cooling requirement is highly intermittent . Thermal storage is motivated by the extreme climatic conditions and the necessity to reduce both max power demand and energy consumption whilst being economically feasible. Thermal storage may be an economically attractive approach to meeting heating or cooling loads if one or more of the following conditions is applied: - Loads have short duration. - Loads occur infrequently. - Loads are not well matched to the availability of the energy source. - Loads are cyclical in nature. - Energy costs are time – dependent. - Energy supply from utility is limited (thus preventing the use of full non storage system. - Utility rebates, tax credits, or other economic incentives are provided for the use of load shifting equipment. The concept behind CTES is simple where water is cooled by chiller during off peak hours and stored in an insulated tank. This stored coolness is then used for space conditioning during hot afternoon hours, using circulated pump and fan in this process.

1.1 Cool Thermal Storage Systems Technology:Cool thermal storage systems can be used to reduce significantly the peak power demand for the AC systems in buildings by allowing energy intensive electrically driven chillers to operate mostly during night time when the electricity rates and demand are lower.

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1.2 Types of Cool Thermal Storage: There are many different types of cool thermal storage systems. They represent various combinations of storage media. a charging mechanism. And a discharging mechanism the available basic media options are water ice, and eutectic salts. We use ice in this project.

1.2.1 Ice Thermal Storage Systems: In ice thermal storage, the latent heat of fusion for water is utilized to store cooling energy. The storage volume is depending on the specific ice storage technology. Since an ice storage system stores cooling energy in ice at 0°C, the freezing point of water. The chiller must be capable of producing charging temperatures of -9.0° C to -3.0° C, below the normal operating range of conventional chillers. The heat transfer fluid in the ice thermal storage systems may be the refrigerant itself or a secondary coolant such as 25% to 40% ethylene glycol mixed with water. The overall energy consumption of ice storage can decrease. Due to the production of low temperature chilled water during the night time. During the night time, the chiller must cool a water-glycol solution to a temperature of between -9.0° C to -3.0° C rather than produce a water temperature of 5.0° C to 7.0° C as for conventional systems. This has the effect of reducing the nominal chiller capacity by approximately 30% to 40%. However, compressor efficiency will vary only slightly because lower night time dry bulb temperatures in the case of air cooled chillers. Result in cooler condenser temperatures and this will help the chillers to operate more efficiently. When using ice storage systems, the size of the chilled water pumps is larger than in conventional system because of the extra head loss resulting from the pressure drop in the ice storage tanks. However, this problem can be overcome by properly designing the storage system with a higher temperature differential. The sizes of the pumps and pipes can be significantly reduced by designing the system with the reduced flow rates that result from using a larger temperature differential in the water loop. Use of a larger temperature range, for example 10.0°C instead of the more traditional 5.5°C temperature range, results a reduction in the water flow rate and therefore reductions in the pumps and pipe sizes as well as their costs. 3

1.2.2 Types of ice thermal storage systems:1.2.2.1 Ice harvesters: An ice harvester system, it is consists of an open insulated storage tank. During charging time, ice is built on the vertical plate surfaces of the evaporator, which are positioned above the storage tank. Water is run by a circulating pump at a temperature of 0.00 C and a flow rate of 0.144 /s to 0.215 /s cooling on the outer surface of the evaporator, which is fed internally with liquid refrigerant. The thickness of the ice build-up on the evaporator plates ranges from 8 nun to 10 min depending on the length of the freezing cycle. The ice is harvested by breaking up the supply of liquid refrigerant by feeding hot gas to the evaporator. This raises the temperature of the outer surface to about 50 C. causing the ice in contact with the plates to melt and fall into the storage tank. The buildup of ice is stopped by a photo-electric switch when the storage tank is fully charged. During the discharging time, the chilled water from the load is circulated through the storage ice tank further reducing the chilled water temperature to cope with the load.

Figure (1.1)

1.2.2.2 Ice slurry: In ice slurry storage system, shown in figure (1.2), Ice particles are generated by passing a weak glycol/water solution approximately ranged between 2% to 10% glycol by mass through tubing that is surrounded by an evaporating refrigerant contained within a shell and tube heat 4

exchanger. As the glycol/water solution is cooled by the evaporating refrigerant, a suspension of ice crystals is formed. The production of small ice particles within a solution of glycol and water can then be pumped or can be dropped directly into the storage tank depending on the system configuration. The ice store discharges by circulating the cool solution from the tank either directly through the AHUs or through an intermediate heat exchanger that isolates the AHUs system from the ice slurry system.

Figure (1.2)

1.2.2.3 Encapsulated ice: An encapsulated ice storage system consists of spheres or rectangular plastic capsules of water immersed in a secondary coolant such as ethylene glycol in a steel or concrete tank. In the united states rectangular containers of approximately 0.017 and 0.0042 size. And dimpled spheres of 100 mm diameter capsules are available. In Europe spheres of 95 mm and 75 mm diameters are also used and are designed to withstand the pressure due to the expansion during freezing. To charge up the storage tank. A low temperature glycol solution (i.e. from -6.0 to 3.0 C) circulates through the tank causing the water in the capsules to freeze by giving up its latent heat. To discharge the storage the warm glycol solution returns from the load to the tank and ice in the capsules melts.

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Figure (1.3) the charging and discharging of encapsulated ice storage

1.2.2.4 External melts ice on coil storage system: The external melt ice-on-coil system is sometimes referred to as an ice builder because in this storage system the ice is formed during the charging time on the outer surface of the heat exchanger coil submerged in an insulated open tank of water as shown in figure (1.4) The coil is made of steel tubing.

Figure (1.4)

During storage charging, liquid refrigerant or a glycol solution circulates inside the heat exchanger coils, causing ice to form on the outside surface of the coils with a thickness of 40mm to 65mm depending on the application. For applications where higher charging temperatures (i.e. 7.00 C to -3.0 C) and greater efficiency are desired, a thinner layer of ice is formed, and for applications where lower charging temperatures (i.e. -12.0 C to -9.0 C) and less efficiency are desired. A thicker layer of ice is formed. During the discharging process, the returned water from the load circulates while passing through the ice tank and cooled down by direct contact with the ice. The charging and discharging processes of the external melt ice-on-coil is illustrated in figure (1.5). 6

Figure (1.5)

1.2.2.5 Internal melt ice on coil storage system: In the internal melt ice on coil storage system, the heat transfer fluid such as a glycol solution circulates through winding coils submerged in tanks filled with water. During charging, the ice forms on the outer surface of the coil when the glycol solution with temperature of -6.0 to -3.0° C flows through the coils inside the tank. During discharging, the warm glycol solution flows through the coil, melting the ice from the inside out and reducing the temperature of the solution for use in meeting the load. The charging and discharging processes of the internal melt ice on coil are shown in figure (1.6).

Figure (1.6)

1.3 Chilled water storage system:Chilled water storage (CWS) systems are unlike ice storage systems in that they rely completely on the sensible heat capacity of the water and the temperature difference between supplies and return water going to and from the cooling load.

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The storage volume required is greater than for any of the ice or eutectic salts storage systems. In the chilled water systems, large storage tanks are used to store chilled water at temperature between 4.0° C and 6.7° C. This temperature is compatible with most conventional cooling systems and allows the use of a conventional chiller. The chillers in these systems cool the water during the night time when the demand for electricity is low and store it in the tank for later use in the day time period when the demand for electricity is high.

Figure (1.7)

1.4 Operation strategies of cool thermal storage systems:Several operation strategies are available for charging and discharging storage to meet cooling load during peak time. The operating strategies of cool thermal storage systems are classified as either full storage or partial storage. Referring to the amount of cooling load transferred or shifted from the night to the day period. Partial storage is further classified into a storage priority and a chiller priority.

1.4.1 Full storage: Full storage system are designed to utilize the stored cooling to shift all building cooling loads from the on-peak period to the off-peak period of the design day. In this operation strategy system, the chiller runs at its full capacity during the night period when the building load is small. 8

In the night period, the chiller charges the storage and meets the building cooling loads simultaneously. Since fill storage systems meet all the building cooling loads during the day time. This will result in larger and therefore more expensive chiller and storage units compared to partial storage systems.

Figure (1.8)

1.4.2 Partial storage systems: In a partial storage system, the chiller operates to meet part of the cooling load and the rest is met by the storage tank during the day time. Usually in this system design, the chiller is sized at a capacity smaller than the design load. Partial storage systems can be further classified based on the selected operation strategies. Load leveling or demand limiting operations. In a load leveling system, the chiller operates at full capacity for 24 hour of the design day. When the building cooling load is less than the chiller capacity, the excess cooling is stored in the storage tank until the tank is filling. When the load exceeds the chiller capacity, the additional cooling is supplied from the storage tank. The load leveling operation is suitable for applications where the peak cooling load is much higher than the average load (i.e. the ratio of peak to average load is high) and the load is high for a long period. It can be designed to minimize the size, and consequently the cost of both the chiller and storage tank. But it reduces the electricity demand during the day time period less than the full storage system does.

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CHAPTER 2 Review of previous work

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Review of previous work Studying the solidification and melting process of water used as phase change material in spherical capsules found to be more useful for is extremely important for the design of efficient cool thermal storage systems. Very limited investigations concerning the cool thermal energy storage (CIES) in encapsulated type are found in literature. They are divided into experimental and theoretical studies.

2.1 Theoretical studies:Isniail et al (1) presented the results of a numerical study on the heat transfer during the process of solidification of water inside a spherical capsule under convective boundary conditions. They formulated the governing equations of the problem and associated boundary conditions. The numerical solution was based upon the finite difference approach and the moving grid scheme. They also validated the numerical predictions by comparison with experimental results realized by the authors. The size of the spherical capsule, wall material, External bath temperature and initial temperature of water were investigated and their effects on the solidified mass fraction and the time for complete solidification were presented and discussed. Cheralatlian et al(2) investigated the transient behavior of phase change material based cool thermal energy storage (CTES). The system discussed was comprised of a cylindrical storage tank filled with encapsulated phase change materials (PCMs) in spherical container integrated with an ethylene glycol chiller plant. A simulation program was developed to evaluate the temperature history of the heat transfer fluid (HTF) and the phase change material at any axial location during the charging period. The results of the model were validated by comparison with experimental results of temperature profiles of HTF and PCM. Bilir et al(3) reported the results of a numerical study on the inward solidification problem of a phase change material (PCM) encapsulated in a cylindrical and spherical container with an initial temperature different than the fusion value. The governing dimensionless equations of the 11

problem and boundary conditions were formulated and solved numerically by using the enthalpy method with control volume approach. It was assumed that the container wall is so thin and its material is so conductive that the thermal resistance through the wall is negligible, the temperature of the coolant fluid and the convective heat transfer coefficient are constant, the heat transfer process inside the container is only by conduction in radial direction, and the densities of solid and liquid phases of PCM are equal. The governing dimensionless equations were solved many times to obtain data sets for different values of the affecting dimensionless parameters, namely, Stefan Number, Biot Number and Superheat parameter. These data then correlated to give total solidification time in terms of these parameters.

2.2 Experimental studies:2.2.1 Pure PCM: Bédécarrats et al(1) make a series of experiments performed to investigate the parameters that effect on storage system consists of a spherical capsules filled with water and a nucleation agent as a Phase Change Material (PCM). Their main obtained results are: - There is a significant influence of the super cooling phenomenon during the charging process. - The lower the inlet coolant temperature and the larger the coolant flow rate are, the faster the storage is. The choice of the couples (flow rate, inlet temperature) must permit to store the total energy in a given time. - When a charge mode follows an incomplete discharge mode, the charge mode is the result of the crystallization of some capsules which present super cooling and of others which do not. The consequence is that the charge mode is made at a higher temperature with a relatively shorter duration. Eames and Adref(2) conducted an experimental study of the freezing and melting processes for water contained in spherical elements. They proposed semi-empirical equations that allow the mass of ice within a sphere to be predicted at any time during the freezing or melting processes. They used a novel method which was used to measure the water–ice interface position during the freezing process. They reported quantitative data on the movement of the solid–liquid interface position 12

with time, the effect of HTF (coolant) temperature, and the effect of sphere size on the melting and freezing processes. They also reported the discharge and charge rates and the time required to melt and freeze a spherical ice storage element. Finally, their results were used to derive empirical equations describing charge and discharge for an ice storage element. Nallusamy et al(3) conducted an experimental evaluation of the thermal performance of a packed bed latent heat thermal energy storage (TES) unit integrated with solar flat plate collector. The TES unit has been developed for the use of hot water at average temperature of 45 °C for domestic applications using packed bed latent heat storage (LHS) concept. The packed bed contained paraffin as phase change material (PCM) filled in spherical capsules, which were put in an insulated cylindrical storage tank. The water used as heat transfer fluid (HTF) to transfer heat from the solar collector to the storage tank also acts as sensible heat storage (SHS) material. Charging experiments were carried out at varying inlet fluid temperatures to examine the effects of porosity and HTF flow rate on the storage unit performance. The performance parameters such as instantaneous heat stored, cumulative heat stored, charging rate and system efficiency were studied. It is concluded that the mass flow rate has significant effect on the heat extraction rate from the solar collector, which in turn affects the rate of charging of the TES tank. Experiments were also conducted for continuous and batch wise discharging processes for both SHS and LHS systems to recover the stored heat, and the results were presented. It was concluded that the packed bed LHS system reduces the size of the storage tank appreciably compared to conventional storage system and that the LHS system employing batch wise discharging of hot water from the TES tank is best suited for applications where the requirement is intermittent. Sakr et al(4) conducted experimental and theoretical study on freezing and melting in capsules with different configurations. They used water as a phase change material (PCM). The PCM was encapsulated in five different copper capsules (sphere, cylinder, pyramid, cone, and cuboid) having the same internal volume. The effect of geometrical configuration on the characterization of the freezing and melting processes was investigated. The spherical capsule showed the best thermal energy storage performance among the five test configurations. For that aspect, the effect of heat transfer fluid (HTF), and mass flow rate on the thermal performance of spherical capsule were further studied. Also, a mathematical model was proposed and solved for the spherical

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capsule. The model results were verified through comparison with the experimental results, and that comparison showed good agreement.

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Chapter 3 Experimental set up

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3.1 Description of the Test Rig:The schematic of the experimental test rig is shown in Figure (3.1). The test rig consists of two loops, one for refrigerant and the other for ethylene glycol solution which is considered as the HTF, the fluid that responsible about adding or removing heat from the PCM that is contained in the spherical capsule (test section).

Figure (3.1) Schematic diagram of the test-rig 1-Evaporator 4- Expansion Valve 7- Rotameter 10- Charging Tank

2- Compressor 5- Pump 8- Discharge Tank

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3- Condenser 6- Gate Valve 9- Test Section

In this chapter we will study the consists of two cycles refrigerant and the Brine cycle as well as the steps of design for each part by details and the material for pipes and the tanks which used in evaporator and The storage tank including the insulation used. 17

3.1. Refrigeration cycle: There are four main components in a refrigeration system: 1234-

The Compressor. The Condenser. The Expansion Device. The Evaporator.

Two different pressures exist in the refrigeration cycle. The evaporator or low pressure, in the "low side" and the condenser, or high pressure, in the "high side". These pressure areas are divided by the other two components. On one end, is the expansion device which controls the refrigerant flow, and on the other end, is the compressor.

3.1.1 Compressor: The compressor is the heart of the system. The compressor does just what its name is. It compresses the low pressure refrigerant vapor from the evaporator and compresses it into a high pressure vapor. The inlet to the compressor is called the “Suction Line”. It brings the low pressure vapor into the compressor. After the compressor compresses the refrigerant into a high pressure Vapor, it removes it to the outlet called the “Discharge Line”. Compressor specification: Reciprocating type (Copeland) Compressor power ==== 2.25 hp Minimum pressure ==== 200 Psi Maximum pressure ==== 20 Psi Model ============= CRC1-0175PFV-501 (USA) 18

3.1.2. Condenser: The “Discharge Line” leaves the compressor and runs to the inlet of the condenser. Because the refrigerant was compressed, it is a hot high pressure vapor (as pressure goes up – temperature goes up). The hot vapor enters the condenser and starts to flow through the tubes. Cool air is blown across the outside of the finned tubes of the condenser (usually by a fan or water with a pump). Since the air is cooler than the refrigerant, heat jumps from the tubing to the cooler air (energy goes from hot to cold – “latent heat”). As the heat is removed from the refrigerant, it reaches its “saturated temperature” and starts to “flash” (change states), into a high pressure liquid. The high pressure liquid leaves the condenser through the “liquid line” and travels to the “expansion device”.

Condenser specification: Forced type ==== cooled by using fan Fan power ==== 1/10 hp RPM

==== 850/950 19

3.1.3. Expansion Device: A very common type of expansion device is called a TX Valve (Thermostatic Expansion Valve). This valve has the capability of controlling the refrigerant flow. If the load on the evaporator changes, the valve can respond to the change and increase or decrease the flow accordingly. The TXV has a sensing bulb attached to the outlet of the evaporator. This bulb senses the suction line temperature and sends a signal to the TXV allowing it to adjust the flow rate. This is important because, if not all, the refrigerant in the evaporator changes state into a gas, there could be liquid refrigerant content returning to the compressor. This can be fatal to the compressor. Liquid cannot be compressed and when a compressor tries to compress a liquid, mechanical Failing can happen.

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Advantage of thermal expansion device than capillary tube: 1- Control in the quantity of the refrigerant through the Expansion device to the evaporator. 2- Give low temperature, reach to -30 C˚.

3.1.4. Evaporators: The last component is the evaporator (tube-in-tube type) which connected with the suction of the compressor where the incoming liquid enters the capillary tube as the pressure is lowered inside and liquid turns to Vapor and that causes the cooling process.

We used Refrigerant (404-a):R-404A is an almost a zoetrope mixture of HFC refrigerants, with zero ozone layer depletion, used in new refrigeration equipment at midrange and low temperatures.

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- Properties:  Average molecular weight (g/mole):  Normal boiling point (F):  Critical temperature (F):  Ozone depletion potential:  ASHRE safety group classification:

- Application: 1- Water coolers 2- Cold stores 3- Refrigerated display cabinets

3.2. Ethylene Glycol cycle: Consists of: 3.2.1. Charging Tank:Dimensions: Height = 80 cm Diameter = 20 cm Test Section= 30 cm

3.2.2. Discharging Tank:Dimensions: Height = 80 cm Diameter = 20 cm Test Section= 30 cm

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97.6 -51.2 161.7 0.0 A1

Test section is the distance between the bottom of the tank and the surface of our solution. Ice balls are placed in tank and a solution is circulated around the balls to freeze them at night and to melt the balls and release the cool energy the following day. We design five levels at equal distances in the ice ball tank and put four thermocouples in each plane.

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3.2.3 Pump:It’s the Device which response to rise the pressure of the Brine and make circulation for this cycle. (It takes flow from the Brine tank and deliver it to the Storage tank). Omega - Model JM100 1HP - Impeller Jet Pump (Centrifugal) Speed of the motor 2850 rpm Suction 9m Power 1 HP Hmax 48 m Qmin 0.3 m³/h. Qmax 2.7 m³/h Hmin 10 m

3.2.5. Pipes:The pipes are made from the (PPR) plastic with a diameter 1 inch.

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 The solution consists of (water+ ethylene glycol) Brine is the result of dissolving Ethylene glycol in water. The mixture cools the balls more rapidly than water and it is better than water because the water will freeze at very low temperatures with respect to water alone (0 c) and that help us to freeze the ice balls at low Temperature.  We can control the limit of freezing of the water by controlling the concentration of the ethylene glycol in water.

Figure (3.3) Curve of the relation between the concentration of Ethylene glycol and the point of freezing of the solution (water + Ethylene)

 We used 35% ethylene glycol in solution by volume.

3.3 Instrumentations & Control Devices:Devices which we used for monitoring controlling.

3.3.1 Thermocouples:Thermocouples are based on the principle that when two dissimilar 25

metals are joined a predictable voltage will be generated that relates to the difference in temperature between the measuring junction and the reference junction (connection to the measuring device).Thermocouples are the most popular temperature sensors .They are cheap, interchangeable, have standard connectors and can measure a wide range of temperatures. The main limitation is accuracy, system errors of less than 1°C can be difficult to achieve. We use (T-type) of thermocouples, names of material are copper (+) and constantan (-), its useful application range is -200-350 oC.

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.3.3.2 Digital Temperature Controller:A digital temperature controller (electronic thermostat) is used to control the required temperature inside the charging or discharging tank during the charging and discharging experiments respectively. The specifications of the digital temperature controller are (ELIWELL IC 901, 0.5 % accuracy, and 1oC set-point differential).

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3.3.3 Data Acquisition System:A data acquisition card (National Instruments, NI USB-6210, 32-inputs, resolution of 16-bit and scanning rate of 250 KS/s) and a laptop are used to record temperatures through aforementioned thermocouples.

3.3.4 Rotameter:The HTF volume flow rate is monitored by using a calibrated rotameter.The rotameter scale is ranged from 1 to 18 Lpm. The rotameter is connected to the common inlet pipe for the charging and discharging tanks. This position is chosen to enable measuring the inlet flow rate to the charging or discharging tank during the charging and discharging experiments respectively. To control a certain flow rate as an experimental parameter; a manual gate valve and a bypass pipe fitted with another manual gate valve are installed before the rotameter. 27

3.3.5 Gate Valve:Used for controlled in the flow rate to the storage tank and keep the quantity of the brine in maintenance case.

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3.4 Insulation:There are two types of insulation used for insulate the Brine cycle:

3.4.1 Fiberglass:Used for insulate (storage tank – Brine tank).

3.4.2 Armaflex:Used for insulate the pipe connection Tube. AP/ Armaflex Pipe Insulation s a flexible thermal insulation made from Elastomeric foam based on synthetic rubber (Elastomeric).

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Chapter 4 Results and Discussion

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The variables that can affect on ice thermal storage packed-bed are: 1- Ball size 2- Ball material 3- Brine inlet temperature 4- Porosity 5- Volume flow rate 6- Concentration ( by volume%) 7- Capsule shape In our experimental test we have studied the effect when we change the flow rate and the inlet brine temperature The water temperature inside the balls decrease with time and solidification occurs at approximately at 0C and to make sure that all water inside the balls is completely solidified the charging process continues and a sub-cooling occurs ( decreasing the temperature below the freezing point ) - Temperature of brine decreases with time when reaching freezing point (sensible heat) - At freezing point approximately ( 0c to -2 ) temperature is constant and the phase change occurs ( latent heat ) - After freezing point the decreases again with time ( sensible heat)

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 Note that :The distance of thermocouples from radial and axial direction for the right hand of the tank

Fig (a) the distance of thermocouples from radial and axial direction for the right hand of the tank

 temperature histories (variation) of balls with time at different radial distances and along the axial direction of the tank under conditions of the Solution flow rate

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- Flow rate 12 L/min , inlet coolant(solution) Temp = -8C˚ (R is radial distance) R=14 mm ,inlet coolant(solution) Temp = -8 C˚, flow rate = 12 L/min

35 30 25 20 15 10 5 0 -5 -10

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Fig (1) Temporal temperature variation at radial location R =14 mm

R= 44 mm , inlet coolant(solution) Temp = -8 C˚, flow rate = 12 L/min 40 30 20 10

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Fig (2) Temporal temperature variation at radial location R = 44mm

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R= 81 mm , inlet coolant(solution) Temp = -8C˚, flow rate = 12 L/min 40 30 20 10

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Fig(3) Temporal temperature variation at radial location R = 81 mm

- Flow rate = 12 L/min , inlet coolant(solution) Temp = -12 C˚

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R= 14 mm , inlet coolant(solution) Temp = -12 C˚, flow rate = 12 L/min 40 30 20 10

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Fig(4) Temporal temperature variation at radial location R = 14 mm

R= 44 mm , inlet coolant(solution) Temp = -12 C˚, flow rate = 12 L/min 40 30 20 10

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Fig(5) Temporal temperature variation at radial location R = 44 mm

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R= 81 mm , inlet coolant(solution) Temp = -12 C˚, flow rate = 12 L/min 40 30 20 T3 10

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Fig(6) Temporal temperature variation at radial location R = 81 mm

- Flow rate = 12 L/min , inlet coolant(solution) Temp = -15 C˚ R= 14 mm ,inlet coolant(solution) Temp = -15 C˚, flow rate = 12 L/min 40 30 20 10

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Fig(7) Temporal temperature variation at radial location R = 14 mm

R= 44 mm , inlet coolant(solution) Temp = -15 C˚, flow rate = 12 L/min 40 30 20 10

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Fig(8) Temporal temperature variation at radial location R = 44 mm

R= 81 mm , inlet coolant(solution) Temp = -15 C˚, flow rate = 12 L/min 40 30 20 10

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Fig (9) Temporal temperature variation at radial location R = 81 mm

- Flow rate = 10 L/min , inlet coolant(solution) Temp = -8C˚ 37

R= 14 mm , inlet coolant(solution) Temp = -8 C˚, flow rate = 10 L/min 40 30 20 10

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Fig (10) Temporal temperature variation at radial location R = 14 mm

R= 44 mm , inlet coolant(solution) Temp = -8 C˚, flow rate = 10 L/min 40 30 20 10

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Fig (11) Temporal temperature variation at radial location R = 44 mm

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R= 81 mm , inlet coolant(solution) Temp = -8 C˚, flow rate = 10 L/min 40 30 20 10

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Fig (12) Temporal temperature variation at radial location R = 81 mm

- Flow rate = 10 L/min , inlet coolant(solution) Temp = -12 C˚ R= 14 mm , inlet coolant(solution) Temp = -12 C˚, flow rate = 10 L/min 40 30 20 10

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75

90

105

Fig (13) Temporal temperature variation at radial location R = 14 mm

R= 44 mm , inlet coolant(solution) Temp = -12 C˚, flow rate = 10 L/min 40 30 20 10

T2

0

T8 T14

-10 0

15

30

45

60

75

90

105

Fig (14) Temporal temperature variation at radial location R = 44 mm

R= 81mm ,inlet coolant(solution) Temp = -12 C˚, flow rate = 10 L/min 40 30 20 10

T3

0

T9 T15

-10 0

15

30

45

60

75

90

105

Fig (15) Temporal temperature variation at radial location R = 81 mm

- Flow rate = 10 L/min , inlet coolant(solution) Temp = -15 C˚

40

R= 14 mm , inlet coolant(solution) Temp = -15 C˚, flow rate = 10 L/min 30 20 10 0

T1

-10

T7 T13

-20 0

15

30

45

60

75

90

105

120

Fig (16) Temporal temperature variation at radial location R = 14 mm

R= 44 mm , inlet coolant(solution) Temp = -15 C˚, flow rate = 10 L/min 30 20 10 0

T2

-10

T8

-20

T14 0

15

30

45

60

75

90

105

120

Fig (17) Temporal temperature variation at radial location R = 44 mm

41

R= 81 mm ,inlet coolant(solution) Temp = -15 C˚ , flow rate = 10 L/min 30 20 10 0

T3

-10

T9 T15

-20 0

15

30

45

60

75

90

105

120

Fig (18) Temporal temperature variation at radial location R = 81 mm

- Flow rate = 8 L/min , inlet coolant(solution) Temp = -8C˚ R= 14 mm , inlet coolant(solution) Temp = -8 C˚, flow rate = 8 L/min 30 20 10

T1

0

T7 T13

-10 0

15

30

42

45

60

75

Fig (19) Temporal temperature variation at radial location R = 14mm

R = 44 mm , inlet coolant(solution) Temp = -8 C˚, flow rate = 8 L/min 30 20 10

T2

0

T8 T14

-10 0

15

30

45

60

75

Fig (20) Temporal temperature variation at radial location R = 44 mm

R= 81 mm ,inlet coolant(solution) Temp = -8 C˚, flow rate = 8 L/min 30 20 10

T3

0

T9 T15

-10 0

15

30

45

60

75

Fig (21) Temporal temperature variation at radial location R = 81 mm

- Flow rate = 8 L/min , inlet coolant(solution) Temp = -12C˚ 43

R= 14 mm , inlet coolant(solution) Temp = -12 C˚, flow rate = 8 L/min 30 20 10

T1

0

T7 T13

-10 0

15

30

45

60

75

90

105

Fig (22) Temporal temperature variation at radial location R = 14 mm

R= 44 mm , inlet coolant(solution) Temp = -12 C˚ , flow rate = 8 L/min 30 20 10

T2

0

T8 T14

-10 0

15

30

45

60

75

90

105

Fig (23) Temporal temperature variation at radial location R = 44 mm

44

R= 81 mm ,inlet coolant(solution) Temp = -12 C˚, flow rate = 8 L/min 30 20 10 T3 0

T9

-10

T15 0

15

30

45

60

75

90

105

Fig (24) Temporal temperature variation at radial location R = 81 mm

- Flow rate = 8 L/min , inlet coolant(solution) Temp = -15 C˚ R= 14mm , inlet coolant(solution) Temp = -15 C˚, flow rate = 8 L/min 30 20 10 0

T1

-10

T7

-20

T13 0

15

30

45

60

45

75

90

105

120

Fig (25) Temporal temperature variation at radial location R = 14 mm

R= 44 mm , inlet coolant(solution) Temp = -15 C˚ , flow rate = 8 L/min 30 20 10 T2

0

T8

-10

T14

-20 0

15

30

45

60

75

90

105

120

Fig (26) Temporal temperature variation at radial location R = 44 mm

R= 81mm ,inlet coolant(solution) Temp = -15 C˚, flow rate = 8 L/min 30 20 10 T3 0

T9

-10

T15

-20 0

15

30

45

60

75

90

105

120

Fig (27) Temporal temperature variation at radial location R = 81 mm

46

 Effect of flow rate on solidification - By increase flow rate the solidification is faster

Flow rate effect 30 25 20 15 10

T1(flow rate 12 L/min)

5 0

T1 (flow rate 10 L/min)

-5

T1 (flow rate 8 L/min)

-10 -15 0

15

30

45

60

75

90

105

120

Fig (28) Temperature variation with time at different flow rate at the same thermocouple

 Calculation of porosity:

porosity 

  

volume of void total volume

Vt  Vb a lls Vt

 1-

Vb alls Vt 47

Total volume for balls =

number of balls . (/6).d 3



 195  / 6 (0.028)3



=0.00224 m3

Volume of storage tank(height of spheres)  (/4). D2 .L  ( / 4).(0.2)2 (0.14) = 0.0044 m3



 1-

0.00224 0.0044

= 0.49

 Energy stored in balls

the amount of heat storage per ball 

 .v.(L.H) time

Assume Phase change at 0 C.

0.8 * 920 * ( / 6)(0.028)3 * 335000 Qball  = 3.144 watt 15 * 60 So, total energy stored= 195*3.144 = 613 watt With neglecting of sensible heat

48

 The other variables and parameters are constant in this study such as: - Ball size ( 28 mm) - The ball material ( plastic ) - Capsule shape ( complete sphere ) - Porosity (48%) - Brine (water + ethylene glycol ) concentration 35% ( by volume)

49

Conclusion Through our experimental test, we have noticed that the parameters which affect the charging time, speed of solidification and energy stored are: 1- Inlet brine temperature 2- Volume flow rate of solution And the results were: 1- By increasing volume flow rate, time of solidification decreases. 2- By decreasing inlet brine temperature, charging time and energy stored in spheres increase.

50

APPENDIX (A)

Thermocouples Calibration

15

Thermocouples Calibration We calibrate thermocouples by using ordinary thermometer. we get a container and put in it cold brine at (-10oc) and fixed the bulb of thermocouple with the bulb of thermometer and put them in the container and we measure the temperature of thermometer and the temperature which thermocouple reading and record them after an equal interval time .then we plot the data on a graph and we got curve fitting for the drawn curve and determine the error In thermocouples (error=±2oC )

25 y = 0.9444x + 0.8896

thermometer( oc)

20

15

Series1 Series2 Linear (Series2)

10

5

0 -10

0

10

20

-5 o

thermocouple( c)

15

30

APPENDIX (B)

Ethylene Glycol Percentage Relative to Freezing point

15

Ethylene Glycol percentage relative to freezing point

15

REFERENCES

55

(1) G. Li, Y. Hwang, Radermacher, “Review of cold storage materials for air conditioning application”, Int. J. Refrig. 35 (8) (2012) 20532077. (2) G. Li, Y. Hwang, R. Radermacher, Chun, "Review of cold storage materials for subzero applications”, Energy 51 (2013) 1-17. (3) Y.H.Yau, Behzad Rismanchi “A review on cool thermal storage technologies and operating strategies”, Renewable and Sustainable Energy Reviews 16 (2012) 787– 797. (4) Guiyin Fang , Shuangmao Wu, Xu Liu,” Experimental study on cool storage air-conditioning system with spherical capsules packed bed” Energy and Buildings 42 (2010) 1056–1062. (5) Ian W. Eames, Kamel T. Adref. “Freezing and melting of water in spherical enclosures of the type used in thermal (ice) storage systems” Applied Thermal Engineering 22 (2002) 733–745. (6) Ismail, K.A.R., Henriquez, J.R., “Numerical and experimental study of spherical capsules packed bed latent heat storage system”, Applied Thermal Engineering, 22 (2002) 1705–1716.

(7) F.L.Tan, S.F. Hosseinizadeh, J.M. Khodadadi , Li wu Fan , “Experimental and computational study of constrained melting of phase change materials (PCM) inside a spherical capsule”, International Journal of Heat and Mass Transfer 52 (2009) 3464– 3472 (8) Nallusamy N., Sampath S., Velraj R., “Study on Performance of a Packed Bed Latent Heat Thermal Energy Storage Unit Integrated with Solar Water Heating System”, Journal of Zhejiang University SCIENCE A, Vol. 7, No. 8, pp. 1422-1430, 2006. (9) K.A.R. Ismail, J.R. Henriquez, T.M. da Silva, “A Parametric Study on Ice Formation Inside a Spherical Capsule”, International Journal of Thermal Sciences, Vol. 42, pp. 881–887, 2003.

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(10) Cheralathan M., Velraj R., Renganarayanan S., “Heat Transfer and Parametric Study of an Encapsulated Phase Change Material Based Cool Thermal Energy Storage System”, Journal of Zhejiang University SCIENCE A, Vol. 7, No. 11, pp. 1886-1895, 2006.

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