A large-scale of district cooling plant could save energy consumption costs from 25% to 40% as compared with the sum of conventional centralized air- conditioning system of each building. In addition to a better energy efficiency, there are other environmental and planning benefits such as, reduced water consumption, reduced carbon footprint, minimized noise and vibration impact, flexibility in building design, saving in plant room space, reduced operating re- dundancy and enhanced system reliability  . District cooling plant supplies cooling services at the temperature level of 5˚C - 7˚C, while with an expected return temperature of 12˚C - 15˚C. The central cooling plant is mostly assisted with a cold thermal storage unit, which allows the leveling of the cooling loads in the network during the day or season and creates a match in supply and demand of cooling services  . Thus, a district cooling network with 8˚C and 15˚C as the supply-return temperature should be an ideal one. Positive to this configura- tion is lower energy loss and higher system efficiency. The energy use in a large district cooling plant before and after the addition of stratified chilled-water sto- rage has been conducted and the average efficiency of the system improved by more than 10% .
Air conditioning systems are considered as an indispensable for life requirements. Most of them are based on vapor compression systems that using R-22 with window type, split units, chillers and heat pumps. Three main types of condensers used in these units are; aircooled, water cooled and evaporative cooling towers. Because the cooling medium (air) is a natural and free source, the aircooledcondensers (ﬁn and tube heat exchangers) mostly used for low and average refrigeration capacities. In these aircooledcondensers, the power consumption is a major issue in vapor compression cycle. The power consumption concern increased much more if the air-cooledcondensers work in area with very high ambient temperature (between 50-60 ⁰C), as it happens in many Middle East countries. In this area, the temperature and pressure of the air-cooled condenser will increased considerably. This causes an increase in pressure ratio which increases the power consumption of the air conditioner. Also, when the pressure increases, the pressure limit in control system will shut down the compressor. The increase of the condenser temperature will decrease the cooling capacity of the cycle due to the reduction of liquid content in the evaporator. So, the high pressure and temperature of the air-cooled condenser will decrease the performance of the air conditioner considerably  .
A condenser or evaporator is a heat exchanger, allowing condensation, by means of giving off, or taking in heat respectively Refrigerant and air will be physically separated, at air conditioner condenser, and evaporator. Therefore, heat transfer occurs by means of conduction. Air-cooledcondensers are increasing in popularity because of the absence of water piping, the consequent simplicity of operation and the freedom from any health risk associated with the use of spray water. One objection to their use is that the capacity of the refrigeration plant does not gradually reduce as the ambient dry-bulb rises but ceases suddenly when the high pressure cut-out operates. A partial solution is to arrange for some of the compressor to be unloaded when the condensing pressure rises, before it reaches the cut-out point. It is a good plan to select air-cooledcondensers to operate in an ambient temperature two or three degree higher than the design value chosen for the rest of the air conditioning system. M. M. Awad et.al studied heat transfer by convection in aircooledcondensers. E.F. Gorzelnik , indulged in the recovery of energy in the heat of compression from air conditioning, refrigeration, or heat-pump equipment in 1977 itself . PSS. Srinivasan et.al. discussed in studies on Waste Heat Recovery from an Air Conditioning Unit that the energy can be recovered and utilized without sacrificing comfort level in 2011. P.Suresh Mohan Kumar Confabulated that he used intercooler which increases the efficiency of Air Conditioning system in 2012. Kaushik and Singh Confabulated about 40 percent of heat is recovered using Canopus heat exchanger in 1995.
Micro channel condenser now days can be effectively used due to its compact size in automobile sector. In this paper review of microchannel condensers can be condenser can be found to be more at various loads and operating conditions. For review same size of microchannel and round tube condenser are considered. From considered and compared with round tube condenser. From the previous experiments the micro-channel condenser was made to have nearly an identical face area, depth and fin density as the round-tube condenser which was the baseline. Also varying the refrigerants, C.O.P & Efficiency of micro channel the various reviews of reviewer micro channel condenser can be efficient and also refrigerator system requires less power.
software ANSYS FLUENT 12.1 is applied to study the flow across the ribbed channel ,The air was the working fluid flow in the channel, and the average heat transfer coefficients were find by measuring overall heat transfer coefficients for the channel. The results showed that the maximum enhancement of average Nusselt number is found to be 3.05 times that of smooth duct for relative roughness height of 0.07. Deepak et al.  investigated the three-dimensional CFD simulations to investigate heat transfer and fluid flow characteristics of artificially roughened rectangular channel using Ansys- CFX. Heat transfer characteristics of the rectangular channel are investigated for Reynolds numbers ranging from 8000 to 18000 . Rectangular channel has an aspect ratio of 5, while the domain length for numerical analysis is kept 550 mm long the hydraulic diameter(Dh) of duct is 66 mm the relative roughness height (e/Dh) is 0.030, relative roughness pitch (p/e) is 10. The results showed the Nusselt number increases as the Reynolds and The Friction factor decreases as the Reynolds number increases . Navanath et al.  presented numerical study of heat transfer in the rectangular duct of cross section 2100x150x200 mm. using different internal ribs (V rib semicircular, Broken V rib 60 degree, Rectangular rib, V rib 60 degree, Rectangular rib with taper, Broken V rib (45 degree) ,Triangular rib , V-rib (45 degree), Triangular broken rib). The software ANSYS FLUENT is applied to study the flow across the ribbed channel. ribs spacing =50mm and pitch to height ratio (rib spacing ) is 8.3 with air as the working fluid at velocity equal to 1 m/s. The results showed the maximum heat transfer coefficient of 78 w/m 2 k for Rectangular taper rib.
Ground granulated blast furnace slag (GGBS) hardens very slowly and, for use in concrete, it needs to be activated by combining it with Portland cement. The greater the percentage of GGBS, the greater will be the effect on concrete properties. The compressive strength of air-cooled blast furnace slag concrete increases with the replacement of fine aggregates by blast furnace slag till 25% replacement after that it gradually decreases. Aircooled blast was used for the replacement of fine aggregate in the percentages 12.5%, 25%, 37.5% and 50%. The compressive strength and flexural strength of air-cooled blast furnace slag concrete increases with the replacement of fine aggregates by blast furnace slag till 25% replacement after that it gradually decreases. The Split tensile strength of the cubes 7days, 56days and 90 days has highest value for 25% replacement and of 28 days has highest value for 12.5% replacement.
Figure 3 presents the graphs of daily voltage and temperature produced for the cooled and uncooled pv system for the period of study. Increase in temperature from 9am-1pm is observed with a decrease in voltage over the same period and this is due to temperature effect on the band gap. At noon, where the ambient temperature and module temperature were highest due to irradiance, both module voltages decreased to the lowest and after that, the voltage increases with decrease in temperature (figure 2). The ac cooling effecton the cooled module increased the total voltage generation by 18% when compared to the uncooled module. These results are similar and in conformity to research work done by [8- 12] using different approach.
Yang et al., 2009 , considered how the chiller performance can be improved by using water mist to pre-cool ambient air entering the condensers to decrease compressor power. A simulation analysis on an air-cooled chiller equipped with a water mist pre-cooling system under head pressure control shows that applying water mist pre cooling enables the coefficient of performance (COP) to increase. They concluded that the application of water mist pre-cooling could increase the COP in various degrees by up to 30%, especially when the relative humidity is low. Furthermore incase of using a water mist system, the chiller power could reduce by 16.2% or 15.8%. Chan et al., 2011 , reported how the coefficient of performance (COP) of air-cooled chillers can be improved by adopting variable condensing set point temperature control and using mist evaporation to pre-cool ambient air entering the condensers to trigger a lower condensing temperature. Chiller models without and with water mist system were established, and the former was validated by using measured operating data of an installed screw chiller. With the validated model, the energy performance of air-cooled screw chillers with twin refrigeration circuits and water mist system serving a representative commercial building was studied. The results reveal that the chiller COP can be changed by various degrees from -0.3% up to +72% depending on the weather and load conditions, and the annual energy consumption can be reduced by 10.9% for a commercial building in subtropical climate
 S.A. Nada, H.F. Elattar, Performance analysis of proposed hybrid air conditioning and humidification dehumidification systems for energy saving and water production in hot and dry climatic regions, Energy Conversion and Management 96 ,(2015) 208–227.
Plants of Prunus laurocerasus (Prunus treatment) grown in 20 L pots were placed around 4 walls (4 plants for the north and 4 plants for the south aspect of each wall). For 3 additional walls, pots containing growing media alone (60% John Innes compost, 20% peat, and 20% perlite), were placed in equivalent locations (Pot+media), to ascertain thermal effects due to the pot/damp media. Finally, 3 other walls had nothing placed in front of them (Control). To avoid bias due to specific locations, the three treatments were re-randomised across the walls every 10 days. All locations irrespective of the presence of plants or not, were irrigated with 4 L of water per day. Air temperatures at the central weather station (ambient) and within the vicinity of the wall (wall) were recorded from 18th Aug until 19th Sep, 2011. Values for 10 min before, on and 10 min after each half-hour interval were used to provide mean values for each wall/location, and data are depicted for diurnal trends between 8.00 and 23.30 (inclusive).
A refrigerator is a common household appliance that consists of a thermally insulated compartment and which when works, transfers heat from the inside of the refrigerator to its external environment so that the inside of the thermally insulated compartment is cooled to a temperature below the surrounding temperature of the room. . Heat rejection may occur directly to the air in the case of a conventional household refrigerator having air-cooled condenser or to water in the case of a water-cooled condenser. Tetrafluoroethane (R-134a) and HC refrigerant was now widely used in most of the domestic refrigerators and automobile air- conditioners and are using POE oil as the conventional lubricant. Heat can be recovered by using the water-cooled condenser and the system can work as a waste heat recovery unit. The recovered heat from the condenser can be used for bathing, cleaning, laundry, etc. The modified system can be used both as a refrigerator and also as a water heater. Therefore by retrofitting a water-cooled condenser it produce hot water and even reduce the utility bill of a small family. It consists of an inlet for the cooling water and an exit for collecting the hot water. The hot water can be used instantly or it can be stored in a thermal storage tank for later use.
Figure 1 shows the relationship between back pressure of steam turbine and ambient temperature for a direct air-cooled unit at full capacity operating. It can be seen from the figure, given the amount of fan flow and heat conditions, the back pressure of steam turbine increased with the ambient temperature increased, the increasing in back pressure steam turbine will cause power generation capacity decline; coupled with environmental strong winds, especially in adverse wind direction angles, wind shear occurred in fan entrance, which will cause back pressure rise further sharp, resulting in a sudden drop in unit load. Meanwhile, the recirculation caused under the environment cross wind, which made the temperature in fan inlet raise, back pressure of steam turbine increase, and even lead to system shutdown.
The exergy loss as well as its ratio of the main four parts with load variation is shown in Figure 8. We can see that the exergy loss of the boiler system is always the maximal for the value, and the second the steam turbine and the air cooling system, and the minimum the regenerative system, and we find that the ratio of the exergy loss of the steam turbine and the regenerative system rises with the increase of the load, while that of the boiler system slowly rises first, then reduc- es. With the load increases, the exergy loss of combustion and heat transfer de- creases, which accounts for most of the exergy loss in the boiler, resulting in a gradual decrease in energy loss at the boiler. In addition, the variation of the ra- tio of the exergy loss for the air cooling system is inconspicuous and is affected by multifarious factors such as environmental parameters, fan operation para- meters, and so on. The exergy efficiency of the steam turbine as well as its three cylinders is shown in Figure 9. Due to the measured parameters fluctuate at low load, so we can see that the exergy efficiency of the three cylinders fluctuates rel- atively obviously at low load, generally less than 350 MW - 400 MW. Because the use of the nozzle adjustment method, it is obvious that the exergy efficiency of the high pressure cylinder averagely appears decreasing with the load increase and when the load rises approximately from 400 MW to 560 MW, its efficiency increases from about 70% to 78%. The exergy efficiency of the whole steam tur- bine with load changing, between about 80% and 85%, is closely related with every cylinder, and the minimum value exists around 300MW to 350MW. Therefore, the unit should be kept away from low load from the point of view of economy or safety.
Window air-conditioner usually been used for a small space area. In this air-conditioner all components, namely the evaporator, compressor, condenser and thermal expansion valve been installed in a single box house. All the components are assembled inside the casing and been install on the wall which casing of the air-conditioner is been fitted into the wall or window of the room. Window air- conditioner can be divided into two compartments which are the room side and the outdoor side. On the room side, the casing is decorated beautifully and consists of supply and return air grills and commonly called as front grill. Outdoor side consists of condenser system in which heat is removed to the atmosphere. Figure 2.2 show type of window air-conditioner.
Datacentres energy consumption constitute a large portion of the global power consumption. Particularly, a large amount of this power is consumed by the datacentre cooling system. Subsequently, many innovated cooling technologies have been developed to reduce the energy consumption and increase the cooling performance. In this work, an experimental setup was designed and constructed which comprises a direct liquid- cooled server, rack-level cooling and compressor-free external cooling system. The study tracks the heat generated from IT processes to the environment. In addition, the power utilization effectiveness (PUE) and the air handling unit (AHU) performance were investigated. These objectives were studied under different datacentre operation scenarios, and AHU configurations.
The characteristics of heat transfer of air-cooled heat exchange depends upon the ability of the fan system to provide sufficient cooling air. Strength and Flow direction often subject peripheral fans to distorted inlet conditions at normal operating conditions with certain reduction in volumetric cooling and flow rate the capacity of cooling. This paper gives the design methodology for single-rotor axial flow fans, suitable for heat exchanger cooling system. The main aim of this work is to solve the issues of robust off-design performance, in particular, distorted inlet flow tolerance. Using this methodology, two 7-bladed and 11 bladed prototype fans were designed, tested and built in accordance with NACA 4609 standards. Axial fans flow handles large volumes of air at relatively low pressures. In general, the manufacturing cost is low and delivers good efficiency, and the shape of the blade is of aerofoil shape. Axial flow fans are operated on high static pressure if required and gives the good efficiency. The main theme is to analyze and model the flow characteristics of AXIAL FANS using CFD Software and draw inference from the obtained results. The performance simulation was estimated using CFD by varying parameters like the blade number, noise level, temperature, velocity, and pressure distribution on the blade surface. This paper aims to present a final 3D solid work model of axial flow fan. Adapting this model to the available components in the market, the first optimization was done. After this step, FLUENT solver is used to do the necessary numerical analyses on the aerodynamic performance of the model. The optimized final result is found which is presented in this article.
exhaust valve as a thermal model of the lumped parameter element to estimate its temperature. Shojaefard et al. [4, 5] have theoretically and experimentally studied the one-dimensional heat transfer at the contact surfaces of two rods that were coaxial. They used the linear system identification method to control the valve temperature. In this method, with the temperatures on both sides of the contact surface, the temperature of the contact region can be estimated theoretically. A thermal contact simulator was used for this purpose. Shojaefard et al.  have conducted an experimental study to determine the thermal contact conductance between two coaxial cylinders, as the exhaust valve and seat. In addition, the effect of contact frequency and contact pressure on thermal contact conductance were studied. The results showed that with increasing frequency, the contact heat transfer coefficient decreases. Mykhaylyk et al.  investigated the thermal contact at the copper-copper contacting surface without coatings in a vacuum environment. Their results showed that the thermal contact initially increases with increasing temperature, then thermal contact decreases with increasing temperature. Dongmei et al.  used the lumped parameter method, which is a transient and a non-contact method for measuring thermal contact resistance between two solids. It was concluded that the thermal contact resistance increases with increasing temperature. The contact pressure can increase the contact area, which can lead to reducing the thermal contact resistance. Shojaefard et al.  investigated the impact of contact frequency and contact pressure on the contact heat transfer coefficient. The results showed that increasing the stiffness of the spring or the contact pressure will increase dramatically the contact heat transfer coefficient. Motahari-Nezhad et al.  carried out the experiments aimed at analyzing thermally the exhaust valve in an air-cooled internal combustion engine for estimating the thermal contact conductance in fixed and periodic contacts. Using the methods of linear extrapolation and the inverse solution, the surface contact temperatures, and the fixed and periodic thermal contact conductance were calculated. Their results showed that the linear extrapolation and inverse methods have similar
velocity of water vapor among the air-cooled condenser tube bundle can lead to Manu problems too, some tube bundle cannot cool all water vapor because of too much intake, at the same time, and some tubes can cool more water vapor than practical intake. For the whole air-cooled condensed, the condensation efficiency is reduced.
A higher load means more burned fuel and results in bigger gas forces and in turn causes larger deformations o f the engine structure. The pressure gradient in the early phase o f the combustion proc ess is more important for the generation and size of the emitted noise. The decrease o f the pressure gra dient during combustion, especially at lower engine speeds, can cause even a 20 dB decrease o f sound pressure [ 6 ] . Noise intensity is increased by 2.5 dB at lower and intermediate engine speeds for the air cooled version - when engine load is increased - and by 1 dB at the engine rated speed. The liquid cooled engine showed a different tendency: there is again an increase in noise intensity with the increase of engine load at lower and intermediate engine speeds. At the rated speed, noise decreases with increase of the engine load. Similar trends have been noted in the past : there is a convergence (similar trends can be seen in figure 9) o f the emitted noise for dif ferent loads at higher engine speeds. One might say that there is a pronounced gradient o f the emitted noise following the increase o f engine load at lower engine speed. On the other hand, at the rated engine speed there is practically no change in noise emis sion with the load change. There is a practical rule for the average increase o f the emitted noise: 30 dB increase can be expected when the engine speed in creases by 10 times [ 6 ] . There is one more feature concerning pressure gradients during the combustion process: the highest pressure gradients can be ex pected at the intermediate engine loads , It can also be seen from figure 9 that the noise o f a liquid cooled engine increases continuously with increasing engine speed and load. Overall reduction o f the emit ted noise when cooling air is replaced by a liquid cool ant amounts to 3 to 5 dB.