An energy-saving and environmentally friendly air-conditioning method has been pro- posed. The key component is a novel indirectevaporative heat exchanger (IEHX) based on the M-cycle. In this design, the compact IEHX is able to produce sub-wet-bulb cooling and reduce the air temperature approaching dew-point temperature. This chap- ter aims to achieve a fundamental understanding of the novel IEHX. A numerical model has been developed and validated by comparing the simulated outlet air conditions against experimental data. The model showed a good agreement with the experimental findings. Employing the validated numerical model, we have theoretically investigated the heat and mass transfer behavior occurred in the IEHX. The detailed cooling process has been analyzed on the psychrometric chart. In addition, the effects of varying inlet conditions and airflow passage dimensions on the cooling efficiency have been studied. By analyzing the thermal performance of the IEHX, we have provided possible sugges- tions to improve the performance of the dew-point cooler and enable it to attain higher cooling effectiveness.
The improvement of refrigeration cycle performance can be done by reducing the compressor work consumption, in- creasing the condenser heat rejection capacity or reducing the difference between condenser and evaporator pressures. Because of its simplicity and compactness window air conditioner is generally used in small size in residential and commercial buildings. The condenser used in this system for heat rejection process which is generally air cooled, it seems reasonable as far as the air temperature in summer is moderate and not too high (about 45º C). But when the air temperature increase and approaches 50º C or higher Window air conditioner that consist of two parts fan coil unit and condensing unit gives poor performance. The performance of window air conditioner depends on heat transfer between the condenser coils and the airflow. Hence by cooling ambient air temperature by evaporativecooling could results in substantial energy and demand saving, this small saving could save considerable amount of watts unit. In air conditioning system generally there are three types of condensers using air cooled, water cooled, and evaporative cooled. Condensers used in small residential Window air conditioners are mostly air cooled condenser.
Fig. 5(a) depicts the impact of inlet air relative humidity on cooling capacity and exergy destruction. It can be seen that the cooling capacity and exergy destruction quickly decrease with varying the inlet air relative humidity from 0.1-0.9. When the relative humidity is low, the driving force for mass transfer caused by water vapor pressure difference between the wet surface and secondary air is greater. Thus, this increases the chance for heat and mass transfer and the exergy destruction is high. The impact of inlet air relative humidity on exergy efficiency, dew point effectiveness and exergy efficiency ratio is shown in Fig. 5(b). The figure shows the exergy efficiency ratio decreases and dew point effectiveness increases as increasing the inlet air relative humidity. The difference between inlet dry bulb temperature and dew point temperature is smaller at high relative humidity, so the dew point effectiveness may increase in a higher relative humidity derived by equation (12). Thus, the dew point effectiveness cannot be considered as a reasonable parameter to characterize the thermal performance of the HMX. When the relative humidity is low, the chemical exergy of inlet air is bigger and the supply air gets more thermal exergy, as the mechanical energy is almost unchanged. Thus, higher exergy efficiency ratio is obtained as the relative humidity is low. Moreover, it can be observed that the exergy efficiency firstly increases towards a maximum value when the inlet air relative humidity is 0.6, and then falls with the increase of inlet air relative humidity. Therefore, both energy and exergy analyses should be considered for the optimization of the process to get the best thermal performance at permissible level of thermodynamic cost.
The experimental results of the evaporativeair cooler prototype were compared against the previous experimental study (Riangvilaikul and Kumar 2010). The comparison was made on the basis of the different operating conditions, structural and geometrical sizes of heat/ mass exchanger. In Fig. 21 and Fig. 22, the rates of decreases in wet bulb and dew point effectiveness with increasing air velocity were similar between the previous experimental study and recent experiment. In previous experimentally study inlet dry bulb temperature and humidity ratio maintained as a 34°C and 19 g/kg respectively.
water-flow rate at all load conditions, which is clearly less energyefficient than the arrangement shown.
Building can be classified into those in which the cooling load is largely constant (mainly dominated internal loads) and those which experience significant variations in load. The building sensible cooling load however, must equal the product of the secondary mass-flow rate, the specific heat of water and the secondary range temperature. In a constant load building, the secondary water-flow rate and secondary range temperature therefore tend to be constant. In a variable load building in which a constant secondary water-flow rate control strategy is adopted, the range temperature tracks the load. However when a variable secondary water-flow rate control strategy is used the range temperature tends to remain approximately constant. These processes can now be examined with reference to Figs. 9 and 10 . In a constant load building the range temperature is constant, the STE falls as the ambient condition falls and the SAT expands as the air-flow rate is reduced in response to a falling ambient AST. This is seen clearly in Fig. 10 where the process of a constant range temperature under conditions of a falling STE and rising SAT are clearly seen. In a variable load building, with a constant secondary water-flow rate the range tempera- ture tends to fall tracking the load while simultaneously the approach temperature rises in response to a falling ambient condition. This results in a sharply falling STE as seen in
was found that maximum effectiveness between 0.55 and 0.706 with concurrently cooling and without cooling it was 0.38 to 0.55, i.e effectiveness of internally cooled packed bed dehumidifier is larger than adiabatic ones. Yonggao Yin et al.  by using LiCl as desiccant studied internally cooled plate fin heat exchanger for dehumidification. The results suggested that plate fin heat exchanger had good cooling performance for the desiccant also low desiccant temperature cause more mass transfer. Improved dehumidification performance can be obtained using simultaneous internal cooling dehumidifier. Yonggao Yin et al. , by using LiCl as liquid desiccant investigated internally cooled dehumidifier and heated regenerator. The study shows that internally heated regenerator will avoid dehumidification risk which might happen in adiabatic one, and additionally it might provide higher regeneration potency that the adiabatic one. The internally cooled dehumidifier may also give higher dehumidification performance examination with adiabatic one, but its profit would be not nearly as good as internally heated regenerator. The commonly used liquid desiccants are inorganic salts like lithium chloride (LiCl), lithium bromide (LiBr) and calcium chloride (CaCl2). LiCl and LiBr are strong desiccants than CaCl2. A therotical model was proposed by I.P. Koronaki et al.  under the same operating condition for a small counter flow adiabatic dehumidifier. LiCl has the best efficiency, can reduce humidity ratio by 10% compared to LiBr 8% and CaCl2 6%. . For cross flow liquid desiccant dehumidifier C. G. Moon et al. , developed new empirical correlation by experimenting dehumidifier with CaCl2 as liquid desiccant. It was found that air flow rate, air humidity ratio, air temperature, solution
The Heat pipe based IEC experimental rig was equipped with a variable speed fan to draw the air at controlled temperature and humidity from an environmental chamber and blow throughout the test-rig, while water is drawn from an overhead tank. Ten thermocouples were installed at several points of the device to measure temperature. Data logger was used to record readings during the experiment and save the data on a computer. The experimental measurements show the air temperature at the outlet of the dry channel is about 26.4°C and that of the wet channel is 25.7°C. It is to be noted that the air temperature in the wet channel did not reach saturation conditions, as it would require a larger wet surface area. This explains the continuous temperature reduction in the wet channel. Figure 4 shows the operating properties of the airflows in the dry and wet channels. It is shown that the outlet air temperature of the dry channel is cooled by about 5°C where the temperature drops from 30 to 25°C. Again, it can be seen that the airflow outlet in the wet channel did not reach the saturation line.
Indirectevaporative coolers (IEC) are components that can be effectively installed in air handling units to increase energy efficiency of air conditioning systems. In particular, such devices can be used in summer conditions to reduce chiller load in both existing and new buildings. In this paper, an IEC system based on a cross flow heat exchanger has been tested, evaluating its cooling capacity in different operating conditions. Performance is evaluated in terms of wet bulb effectiveness, primary air temperature reduction and fraction of evaporated water. Results put in evidence that a significant cooling capacity can be achieved in many operating conditions. Therefore, IECs are a promising technology that can be effectively used to reduce primary energy consumption of conventional systems.
2 INTERNATIONAL JOURNAL OF EMERGING TECHNOLOGY AND ADVANCED ENGINEERING “Design Optimization and Installation of the Evaporative Cooler.”, Md. Almostasim Mahmud, Dr. Md. Alamgir Hossain, M.A.Muktadir : This Evaporativecooling is an environmentally friendly aircooling system that operates using induced processes of heat and mass transfer, where water and air are the working fluids. It consists, specifically, in water evaporation, induced by the passage of an air flow, thus decreasing the air temperature. In Bangladesh, Evaporative cooler is already being used in different industries that is imported from varies countries. But most of the cases these are not efficient due to installation error & lack of adjustment with climate change over the year. Initially this paper presents the construction of an evaporative cooler using a test bench of cooling tower for the air flow and water supply facility where local materials were used as evaporative pad. Afterwards; it presents installation in different situation & adjustment of the cooling units with the climate. It concludes that under proper installation, evaporativecooling system is very cost effective & has a very large potential to propitiate thermal comfort and can still be used as an alternative to conventional systems in regions where the design wet bulb temperature is low.
have explored droplet evaporation and air temperature under different loading conditions, solution and spray features. They found that using very fine droplets ranging between 25 and 50 μm results in a significant aircooling. Optimal conditions have between sought regarding their size, as too small droplets where found to flow in a concentrated manner with a poor dispersion ability resulting in a less effective mixing, despite their better expected capacities when considered as individual particles. The counter flow injection is found to provide a more efficientcooling of the air. A study of heat transfer enhancement using an air flow containing water droplets across a heat exchanger has been carried out by Boulet et al.  . They showed that spray
Qi et al. (2013) proposed a prediction model for an internally cooled and heated LD system. This prediction model can define three types of effectiveness of an internally cooled and heated LD system: enthalpy, moisture, and temperature effectiveness. In addition, the system outlet parameters of all fluids including the air, desiccant solution, and heating or cooling fluid can be calculated accurately under different operating conditions. Zhang et al. (2013) examined an ICLD dehumidifier using a fin and tube heat exchanger. They analyzed the performance of the ICLD dehumidifier using performance indicators, namely, the moisture removal rate, dehumidification effectiveness, and volume mass transfer coefficient, to evaluate the system performance. Based on the results of this study, the experimental data agree well with previous studies and a numerical model with an error bound of 20%.
performance and COP was analyzed as shown in Fig. 5 and Table 1, respectively. The results showed that the dehumidification performance by the system was improved with the increase in regeneration temperature but the supply air temperature was also increased. Furthermore, the system COP started decreasing from 0.44 to 0.35 with the increase in regeneration temperature from 60 to 75 °C as shown in Table 1. It was concluded that the thermal heat supplied to the DAC system is not exactly proportional to the final cooling effect. Therefore, an optimum regeneration temperature is required to obtain efficient performance of a DAC system.
Recently, a new hybrid air-conditioning system consisting of IEC and mechanical cooling has been proposed for IEC application in hot and humid regions. The IEC, installed before an AHU, is used to pre- cool the incoming fresh air for energy conservation of the air-conditioning system. In this system, the cool and dry exhaust air from air-conditioned space is used as secondary air. However, due to the high humidity of the fresh air in humid areas, condensation probably occurs, which results in not only sensible cooling but also dehumidification effect. The IEC modeling with condensation from primary air has seldom been reported by previous studies. Besides, a sensitivity parameter study under IEC condensation state is also lacking.
condition, an indirectevaporativecooling system applied to packaged unit air conditioner and they are able to improve the cooling load up to 75% and consume 55% less electrical energy. Delfani Shahram, (2010). Zhang et al., (2000), carried out a study on the evaporative cooler permeated with corrugated holed aluminium foil and given relationship to estimate the performance, pressure drop and outlet air temperature of the cooler. They apply the relationship for estimate the enhancement of an air-cooled chiller by analyze the exit temperature of evaporative cooler with the performance curve of the chiller and conclude that the COP for chiller could be enhanced about 39%. An air-cooled chiller coupled with a direct evaporative cooler able to reduce 14.4% in power consumption and increase the refrigeration capacity about 4.6%. Yu and Chan, (2005).
Response: Federal Aviation Regulation (FAR) Part 91 specifies that pilots operating under Visual Flight Rules (VFR) are primarily responsible for navigation, obstacle clearance and maintaining separation from other aircraft using the see-and-avoid concept. To avoid collisions, the VFR pilot is expected to "see and avoid" obstacles and other aircraft. A pilot that was successful in visually acquiring the airfield for landing would have no difficulty seeing and safely avoiding the Troutdale Energy Center stacks. From an air traffic control standpoint, air traffic controllers will therefore not be required to direct aircraft solely to the south pattern. 4. OPA asserts the following: “At night, the unlighted and invisible thermal plume will be impossible for airmen to identify and avoid, and unable to exercise the caution that is required by the instructions in the AIM, all nighttime operations must be conducted in the south traffic pattern. Nighttime use of the south pattern increases risk of collision with terrain since an unlighted 720 foot bluff (Broughton Bluff) lies beneath the south downwind to base turn.”
The building cooling load is calculated according to the building specification and construction materials. Figure 1 shows the layout of two types of buildings, the first is residential buildings and hotels; the second is schools and govern- mental buildings. Two Models A and B were used for the two types of buildings. The buildings Model A is constructed from common materials; hollow bricks, heavy concrete, single layer glazed windows, and wooden doors as illustrated in Figure 2, but the buildings Model Bistypical as Model A of construction mate- rials in addition of 5 - 8 cm thermal insulation of 0.039 W/m·K in outside walls, floor, ceiling and glazed windows with double layers of air gab 1 - 3 cm. The peak or maximum building heat load is estimated at 3 o’clock PM for outside condition of 45˚C dry bulb and 28˚C wet bulb and inside condition of 24˚C dry bulb and 50% relative humidity.
One historical name for some types of EAC's is an "air washer". Although some older versions of air washers were not very efficient at cleaning tiny particulate from the air stream, they would catch and wash down some dust and larger particulates. Newer evaporative pads with denser media are better at washing the air, but still are not as efficient as typical air filter media. The tradeoff for high filtration efficiency is the pressure drop across the filtering media that the supply fan has to overcome, thus using more fan energy. The newer 12 to 18" thick (in the direction of air flow) rigid media is much more efficient at filtration because it has two methods of air filtration. First is the fluted bend inside the cardboard media that makes the air change direction slightly. When the air molecules change direction, the heavier dust particles can't turn as fast, and impact on the media wall (known as an inertial mass separator). The second stage to the filtration is the wet surface where the dust particle impacted. Through surface tension, it holds on to the dust, and eventually is washed into the sump (known as a viscous impingement filter, like your nose). While evaporative media is not designed to operate as a filter, the 12" rigid media when wet will capture over 90% of particles 5-10 microns or larger, according to test information from Munters Corp., a manufacturer of rigid media. “Fungus spores are usually from 10 to 30 micron, while pollen grains are from 10 to 100 micron, with many common varieties in the 20 to 40 micron range… Particles larger than 8 to 10 micron in diameter are separated and retained by the upper respiratory tract”. 33 See Figure 20 for the for the particle size efficiency graph.
In the following, various equipments presently being used in various locations, both in rural and urban sectors, are briefly described. If we study various air flow equipment, normal hand fans and electric fans cannot give great comfort as its role is limited. They only push the air from one place to the other. It has no mechanism to reduce the temperature in an area. Air coolers are more efficient than normal electric fans. It contains the water circulation in a small area and thus reduces the temperature of the ambient air. This cooled air will be pushed from a small enclosed area to the room and thus reduces the room temperature. The commercially available air coolers in recent years have two basic electric motors. One motor pumps the water from lower level to the upper level of about 3 to 4 feet. Another motor drives the air from inside to outside, in a similar fashion as that of a normal electric fan. The air conditioning system has a compressor as additional equipment. The air from the at- mosphere is compressed in the compressor and released into the atmosphere in a controlled fashion. This way the compressed air under high pressure when released to the normal atmospheric pressure, expands and thus the temperature of the air decreases. This is due to the well-known phenomena called “Joule Thomson Effect”. In recent years, split air conditioning equipment has become more popular. In this system, there are two equip- ments. One is the compressor unit with air intake and another is the air blower with controllers. It is pertinent to say that the air conditioning equipment, although more comfortable than all other equipment, consumes large power. Traditional air cooler, although give comfort by reducing air temperature, it has a problem of humidity. It increases the moisture in the air. After a period of use, the discomfort level increases due to moisture effect on the skin. More importantly, it is not effective in high humid regions such as coastal regions. In such a scenario, the time has come to develop efficient, low energy equipment for thermal comfort.
However the important issue, in this respect, is the annual energy efficiency of the process rather than any specific diurnal efficiency. As the chilled ceiling system generally operates at a constant cooling water flow temperature, the annual energy efficiency can be greatly improved by taking advantage of lower ambient wet bulb temperatures (WBT) in the non-Summer months to increase the SAT by using a modulated reduction in fan speed, such as is provided by an inverter controlled motor. Hence chilled ceiling systems, which can currently operate with a cooling water temperature as high as 18°C, (CIBSE 1998) can be supplied by evaporativecooling systems with a SAT ranging from 11 K in Winter to 3 K in Summer. The lower limit of the process is dictated by the minimum fan motor speed compatible with heat dissipation from the motor windings. Furthermore as the evaporativecooling technique rejects only the cooling load, without the addition of the heat of compression (as would be the case with refrigeration based cooling systems) the process is, also in this respect, inherently more energyefficient than the vapour compression cycle.
One system cools and humidifies multiple zones with separate demands
Fan-assisted dispersion Fan assisted fans have a hub style design for localized access and more efficient evaporation as it mores air more effectively. The fan-assisted dispersion unit pulls the air from above where it tends to be warmer.
Cools and humidifies in air handlers, ducts, and open spaces