scholarly journals Adaption of an Evaporative Desert Cooler into a Liquid Desiccant Air Conditioner: Experimental and Numerical Analysis

Atmosphere ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 40 ◽  
Author(s):  
Mustafa Jaradat ◽  
Mohammad Al-Addous ◽  
Aiman Albatayneh
Keyword(s):  
Indoor Air ◽  
Operating Cost ◽  
Dew Point ◽  
Air Conditioner ◽  
Liquid Desiccant ◽  
Human Thermal Comfort ◽  
Effectiveness Model ◽  
Air Cooler ◽  
Maximal Deviation ◽  
Air Conditioning Systems

Desert coolers have attracted much attention as an alternative to mechanical air conditioning systems, as they are proving to be of lower initial cost and significantly lower operating cost. However, the uncontrolled increase in the moisture content of the supply air is still a great issue for indoor air quality and human thermal comfort concerns. This paper represents an experimental and numerical investigation of a modified desert air cooler into a liquid desiccant air conditioner (LDAC). An experimental setup was established to explore the supply air properties for an adapted commercial desert cooler. Several experiments were performed for air–water and air–desiccant as flow media, at several solutions to air mass ratios. Furthermore, the experimental results were compared with the result of a numerical simplified effectiveness model. The outcomes indicate a sharp reduction in the air humidity ratio by applying the desiccant solutions up to 5.57 g/kg and up to 4.15 g/kg, corresponding to dew point temperatures of 9.5 °C and 12.4 °C for LiCl and CaCl2, respectively. Additionally, the experimental and the numerical results concurred having shown the same pattern, with a maximal deviation of about 18% within the experimental uncertainties.

scholarly journals Indoor Air Quality Enhancement Performance of Liquid Desiccant and Evaporative Cooling-Assisted Air Conditioning Systems

2019 ◽  
Vol 11 (4) ◽  
pp. 1036 ◽  
Author(s):  
Beom-Jun Kim ◽  
Junseok Park ◽  
Jae-Weon Jeong
Keyword(s):  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Reference System ◽  
Air Conditioning ◽  
Evaporative Cooling ◽  
Quality Enhancement ◽  
Liquid Desiccant ◽  
Air Conditioning Systems ◽  
Indoor Pm2.5

The main objective of this study is to investigate the indoor air quality enhancement performance of two different liquid desiccant and evaporative cooling-assisted air conditioning systems, such as the variable air volume (VAV) system with the desiccant-enhanced evaporative (DEVap) cooler, and the liquid desiccant system with an indirect and direct evaporative cooling-assisted 100% outdoor air system (LD-IDECOAS), compared with the conventional VAV system. The transient simulations of concentration variations of carbon dioxide (CO2), coarse particles, and fine particles (PM10 and PM2.5) in a model office space served by each system were performed using validated system models that were found in the literature. Based on the hourly thermal loads of the model space predicted by the TRNSYS 18 program, each air conditioning system was operated virtually using a commercial equation solver program (EES). The results indicated that the LD-IDECOAS provided the lowest annual indoor CO2 concentration among all the systems considered in this research, while the VAV system with DEVap cooler exceeded the threshold concentration (i.e., 1000 ppm) during the cooling season (i.e., July, August, and September). For the indoor particulate contaminant concentrations, both liquid desiccant and evaporative cooling-assisted air conditioning systems indicated lower indoor PM2.5 and PM10 concentrations compared with the reference system. The LD-IDECOAS and the VAV with a DEVap cooler demonstrated 33.3% and 23.5% lower annual accumulated indoor PM10 concentrations than the reference system, respectively. Similarly, the annual accumulated indoor PM2.5 concentration was reduced by 16% using the LD-IDECOAS and 17.1% using the VAV with DEVap cooler.

Exergy Analysis of Energy Consumption for Central Air Conditioning System

2014 ◽  
Vol 628 ◽  
pp. 332-337
Author(s):  
Xiao Xia Xia ◽  
Nai Jun Zhou ◽  
Zhi Qi Wang
Keyword(s):  
Energy Consumption ◽  
Air Conditioning ◽  
Exergy Analysis ◽  
Exergy Efficiency ◽  
Dew Point ◽  
Exergy Loss ◽  
Air Conditioning System ◽  
Air Cooler ◽  
Central Air Conditioning ◽  
Air Conditioning Systems

The energy consumption of several central air conditioning systems in summer was researched by the method of exergy analysis. Combined with actual example,the exergy loss of all the equipments and the exergy efficiency of three systems were calculated. The results show that the exergy efficiency of three systems is very low. Relatively speaking, the exergy efficiency of primary return air conditioning system with supplying air in dew point is highest. The equipment of highest exergy loss is air-conditioned room, while the exergy loss of surface air cooler is smallest. Based on this, several improvement measures were proposed to reduce exergy loss and improve exergy efficiency.

scholarly journals Energy Performance Comparison between Two Liquid Desiccant and Evaporative Cooling-Assisted Air Conditioning Systems

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 522
Author(s):  
Su Liu ◽  
Jae-Weon Jeong
Keyword(s):  
Energy Consumption ◽  
Air Conditioning ◽  
Evaporative Cooling ◽  
Dew Point ◽  
Outdoor Air ◽  
Liquid Desiccant ◽  
Energy Saving Potential ◽  
Evaporative Cooler ◽  
Air Conditioning Systems ◽  
Direct Evaporative Cooler

This study investigated the annual energy saving potential and system performance of two different evaporative cooling-based liquid desiccant and evaporative cooling-assisted air conditioning systems. One system used an indirect and direct evaporative cooler with a two-stage package to match the target supply air point. The other was equipped with a single-stage, packaged dew-point evaporative cooler that used a portion of the process air, which had been dehumidified in advance. Systems installed with the two evaporative coolers were compared to determine which one was more energy efficient and which one could provide better thermal comfort for building occupants in a given climate zone, using detailed simulation data. The detailed energy consumption data of these two systems were estimated using an engineering equation solver with each component model. The results showed that the liquid desiccant and dew-point evaporative-cooler-assisted 100% outdoor air system (LDEOAS) resulted in approximately 34% more annual primary energy consumption than that of the liquid desiccant and the indirect and direct evaporative-cooler-assisted 100% outdoor air system (LDIDECOAS). However, the LDEOAS could provide drier and cooler supply air, compared with the LDIDECOAS. In conclusion, LDIDECOAS has a higher energy saving potential than LDEOAS, with an acceptable level of thermal comfort.

scholarly journals A Zero Carryover Liquid-Desiccant Air Conditioner for Solar Applications

Solar Energy ◽  
2006 ◽  
Author(s):  
Andrew Lowenstein ◽  
Steve Slayzak ◽  
Eric Kozubal
Keyword(s):  
Indoor Air ◽  
Mass Exchange ◽  
Energy Efficient ◽  
Low Flow ◽  
Air Conditioner ◽  
Liquid Desiccant ◽  
Heat And Mass Exchange ◽  
Pressure Drops ◽  
Simultaneous Heat ◽  
Contact Liquid

A novel liquid-desiccant air conditioner that dries and cools building supply air has been successfully designed, built and tested. The new air conditioner will transform the use of direct-contact liquid-desiccant systems in HVAC applications, improving comfort and indoor air quality, as well as providing energy-efficient humidity control. Liquid-desiccant conditioners and regenerators are traditionally implemented as adiabatic beds of contact media that are highly flooded with desiccant. The possibility of droplet carryover into the supply air has limited the sale of these systems in most HVAC applications. The characteristic of the new conditioner and regenerator that distinguishes them from conventional ones is their very low flows of liquid desiccant. Whereas a conventional conditioner operates typically at between 10 and 15 gpm (630 and 946 ml/s) of desiccant per 1000 cfm (0.47 m3/s) of process air, the new conditioner operates at 0.5 gpm (32 ml/s) per 1000 cfm (0.47 m3/s). At these low flooding rates, the supply air will not entrain droplets of liquid desiccant. This brings performance and maintenance for the new liquid-desiccant technology in line with HVAC market expectations. Low flooding rates are practical only if the liquid desiccant is continually cooled in the conditioner or continually heated in the regenerator as the mass exchange of water occurs. This simultaneous heat and mass exchange is accomplished by using the walls of a parallel-plate plastic heat exchanger as the air/desiccant contact surface. Compared to existing solid and liquid desiccant systems, the low-flow technology is more compact, has significantly lower pressure drops and does not “dump” heat back onto the building’s central air conditioner. Tests confirm the high sensible and latent effectiveness of the conditioner, the high COP of the regenerator, and the operation of both components without carryover.

scholarly journals Fungal colonization of air-conditioning systems

2008 ◽  
Vol 60 (2) ◽  
pp. 201-206 ◽  
Author(s):  
Milica Ljaljevic-Grbic ◽  
Jelena Vukojevic ◽  
M. Stupar
Keyword(s):  
Aspergillus Fumigatus ◽  
Indoor Air ◽  
Air Conditioning ◽  
Fungal Colonization ◽  
Air Conditioner ◽  
Volatile Organics ◽  
Hospital Environments ◽  
Indoor Fungi ◽  
Air Conditioning Systems ◽  
Human Infections

Fungi have been implicated as quantitatively the most important bioaerosol component of indoor air associated with contaminated air-conditioning systems. rarely, indoor fungi may cause human infections, but more commonly allergenic responses ranging from pneumonitis to asthma-like symptoms. From all air conditioner filters analyzed, 16 fungal taxa were isolated and identified. Aspergillus fumigatus causes more lethal infections worldwide than any other mold. Air-conditioning filters that adsorb moisture and volatile organics appear to provide suitable substrates for fungal colonization. It is important to stress that fungal colonization of air-conditioning systems should not be ignored, especially in hospital environments.

Experimental and Theoretical Study of Liquid Desiccant Dehumidification System by Using the Effectiveness Model

2012 ◽  
Vol 4 (1) ◽  
Author(s):  
Hassan Pahlavanzadeh ◽  
Parisa Nooriasl
Keyword(s):  
Mass Transfer ◽  
Lithium Chloride ◽  
Packed Bed ◽  
Air Conditioner ◽  
Liquid Desiccant ◽  
Effectiveness Model ◽  
Transfer Unit ◽  
Predicting Performance ◽  
Cooling Air ◽  
Evaporation Cooling

Desiccant evaporation cooling technology is compatible with the environment and can be used as an air conditioner in the indoor environment of the buildings. The characteristics of dehumidification column of the liquid desiccant evaporation cooling air conditioning system (LDCS) are introduced in this paper. This system was designed and manufactured for this purpose. Lithium chloride (LiCl), as liquid desiccant, and a packed bed column were used for the dehumidification. The described system includes a part for processed air simulation in various temperatures, humidities, and flow rates. The effectiveness model, based on heat and mass transfer equations, is considered for predicting performance of the lithium chloride dehumidification system. For validation purpose, a comparison was performed between experimental outlet data of the system and the corresponding results of the experimental model that showed a satisfactory correlation i.e., increase in the mass transfer unit number (NTU) leads to a better performance of the dehumidification system. In addition, factors leading to increase in NTUs are also investigated.

Numerical and Experimental Modeling of Indoor Air Quality Inside a Conditioned Space with Mechanical Ventilation and DX-Air Conditioner

2020 ◽  
Vol 38 (9A) ◽  
pp. 1257-1275
Author(s):  
Wisam M. Mareed ◽  
Hasanen M. Hussen
Keyword(s):  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Ventilation System ◽  
Thermal Conditions ◽  
Airflow Rate ◽  
Air Conditioner ◽  
Breathing Zone ◽  
Lecture Room ◽  
Ventilation Performance

 Elevated CO2 rates in a building affect the health of the occupant. This paper deals with an experimental and numerical analysis conducted in a full-scale test room located in the Department of Mechanical Engineering at the University of Technology. The experiments and CFD were conducted for analyzing ventilation performance. It is a study on the effect of the discharge airflow rate of the ceiling type air-conditioner on ventilation performance in the lecture room with the mixing ventilation. Most obtained findings show that database and questionnaires analyzed prefer heights between 0.2 m to 1.2 m in the middle of an occupied zone and breathing zone height of between 0.75 m to 1.8 given in the literature surveyed. It is noticed the mismatch of internal conditions with thermal comfort, and indoor air quality recommended by [ASHRAE Standard 62, ANSI / ASHRAE Standard 55-2010]. CFD simulations have been carried to provide insights on the indoor air quality and comfort conditions throughout the classroom. Particle concentrations, thermal conditions, and modified ventilation system solutions are reported.

A Novel Window Type Air-Conditioner with Energy Recovering

2011 ◽  
Vol 250-253 ◽  
pp. 3021-3024
Author(s):  
Qing Hai Luo ◽  
Peng Fei Zhang ◽  
Xiu Fei Yang ◽  
Jun Zou
Keyword(s):  
Energy Efficiency ◽  
Heat Exchanger ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
The Other ◽  
The Novel ◽  
Air Conditioner ◽  
Efficiency Ratio ◽  
Additional Heat ◽  
Experimental Prototype

A novel window type air-conditioner with energy recovering was experimented. The experimental prototype can make fresh air exchange heat with exhaust air in an additional heat exchanger, which consist no additional moving parts. The EER (energy efficiency ratio) of the experimental air-conditioner (EAC) is increased by 17.4~37.3% than that of the original ordinary window type air-conditioner (OAC). On the other hand, the fresh air proportion of the EAC is increased by 20% or so than that of the OAC, so indoor air quality can be greatly improved via the EAC; however the indoor noise of the EAC is increased by 3.2 dB or so. The novel experimental prototype is of great significance for energy efficiency.

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