Absorcare Desiccant

This work presents results of experimental and simulation study of a solar assisted pre-cooled hybrid desiccant cooling (PHDCS) system for air conditioning applications in Pakistan. Tests were conducted on a gas fired pre-cooled hybrid desiccant cooling test rig for high humidity Karachi weather. Using measured data sets from the test rig, validation of TRYNSIS model of the same cooling system was undertaken. Four modes or configurations of the cooling system were simulated for Karachi and Lahore climatic conditions. Lahore simulation results demonstrated that better COP_p can be achieved using indirect evaporative cooler for pre-cooling and direct evaporative cooler for post-cooling of air. Life cycle assessment of solar air collector was performed and energy and environmental payback periods were found to be equal to 1 and 1.5 years, respectively. An economic assessment of the solar collector revealed a payback period of about 14 years.

A. Khalid?M. Mahmood?M. Asif?T. Muneer
Energy Conservation Lab, Mechanical Engineering Department, NED University of Engineering & Technology, Main Campus, University Road, 75300 Karachi, Pakistan

A desiccant wheel model has been developed in the aim to be adapted to building simulation tools. This model fulfils several criteria such as simplicity of parameterization, accuracy, possibility to characterize the equipment under all operation conditions and low computation time. The method of characteristics has been applied to the heat and mass transfer partial differential equations. This transformation provides new equations which are similar to those of a rotary heat exchanger. Then, the model is described by the Effectiveness-NTU method and it is identified from only one nominal rating point. The model has been compared to experimental and manufacturers’ data for a broad range of operating conditions. A good agreement has been found.

Pascal Stabat?Dominique Marchio
Ecole des Mines de Paris -Centre Energetique et Procedes, 60 boulevard Saint Michel, F 75272 Paris cedex 06, France

A method for the determination of dimethyl fumarate (DMF), benzothiazole (BT) and tert-butylphenol (TBP) in desiccant and antimould agents employed for protecting consumer products from humidity and mould has been developed. The method is based on ultrasound-assisted extraction (UAE) followed by GC-MS analysis. Parameters that could affect the extraction of the compounds have been optimised using a multivariate approach. In the final conditions, the extraction is performed using only 0.5 or 1 mL ethyl acetate and applying ultrasound energy for 5 min. Simultaneous extractions could also be carried out in 5 min without losing efficiency. The method was validated showing good linearity (R 2 >0.995). Both intra- and inter-day precisions were studied at several concentration levels, being satisfactory in all cases (RSD <10%). Recovery was evaluated in four real desiccant samples at different compound concentrations, ranging between 87% and 109%. Limits of detection and quantification were in the low nanogramme per gramme level, thus allowing the determination of DMF at concentrations well below the limit established by the recent EU Directive (0.1 ?g/g). The proposed procedure was applied to the determination of the target compounds in several desiccant and antimould samples. Although most of them were simply labelled as “silica gel”, more than 70% of the tested samples contained high amounts of DMF, many of them at the high microgram per gramme level. Many samples also showed the presence of the other two potential allergens. These results demonstrate that the content of the “desiccant” sachets and tablets in consumer products does not usually belong with the label of the desiccant, and hence, the high risk of exposition to the powerful allergen DMF and other potentially harmful chemicals through consumer goods should be a matter of concern.

J. Pablo Lamas1?Lucia Sanchez-Prado1?Jorge Regueiro1?Maria Llompart1?Carmen Garcia-Jares1
[1] Departamento de Quimica Analitica, Nutricion y Bromatologia, Facultad de Quimica, Instituto de Investigacion y Analisis Alimentario, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain

A multiform coated solid form(CSF)closure system for HDPE pharmaceutical bottles has been announced by Multisorb Technologies of Buffalo,NY,USA in partnership with Neutroplast Industria de Embalagens Plasticas,SA.The system combines Multisorb’s Multiform CSF concentrated desiccant with Neutroplast’s screw closure.

A potentially quicker total weed-killer was among the new solutions demonstrated by Agrovista at its open day last week. Mike Abram reports. Pesticide manufacturer Nichino is seeking approval for a new des-iccant that Agrovista intends to target at the stale seed-bed herbicide market. A co-formulation of glyphosate and a new desiccant, pyraflufen-ethyl, its advantages in trials had been a much faster speed of kill and better control of difficult weeds, Agrovista technical manager Mark Hemmant told Farmers Weekly at the firm’s open day at Stoughton, Leicestershire.

This paper presented the characteristic of liquid desiccant dehumidirication based on NTU~Le model. The results showed that the Lewis number Le had little effect on air outlet humidity ratio during desiccant solution dehumidirication process. A new method called h{sub}D-Le separative evaluation method was developed for determining coupled heat and mass transfer coefficients between air and liquid desiccant, through which the heat and mass transfer coefficients between air and liquid desiccant were calculated to obtain from experimental inlet and outlet parameters of air and desiccant solution. The effects of the air volume flow rate, temperature, humidity ratio and the solution concentration, temperature on the Lewis number, heat and mass transfer coefficient were analyzed according to experimental data and the h{sub}D-Le separative evaluation method. Based on the computation results, it was concluded that the Lewis number greatly depended on the operation parameters and conditions of the air and desiccant. In addition, the correlations of the heat and mass transfer coefficients were developed. The additional 74 groups of experiments validated the developed correlations by comparison of air/solution parameters change with the calculation data.

Yonggao Yin?Xiaosong Zhang

Heat and mass transfer between air and liquid desiccant in a cross-flow packed bed dehumidifier is investigated. Analytical solutions of air and desiccant parameters as well as enthalpy and moisture efficiencies are given in the present study, based on the analogy between the combined heat and mass transfer process in the cross-flow dehumidifier and the heat transfer process in the cross-flow heat exchanger. The results given by the analytical solution are compared with numerical solutions and experimental findings. Good agreement is shown between the analytical solutions and the numerical or experimental results. The analytical solutions can be used in the optimization of the cross-flow dehumidifier.

Xiao-Hua Liu?Yi Jiang?Kai-Yang Qu

This article introduces a liquid desiccant fresh air processor. Its driving force is low-grade heat (heat obtained from 65 – 75°C hot water). Inside the processor, the air is dehumidified by the evaporative cooling energy of the indoor exhaust air. A four-stage structure is used to increase the efficiency of the combined sensible and latent heat recovery from the exhaust air. A mathematical model of the fresh air processor was set up using Simulink®. A liquid desiccant fresh air processor was constructed and tested for outside air conditions of 29.1 – 33.6°C, 13.7 – 16.7g/kg humidity ratio, and supply air conditions of 23.6 – 24.2°C, 7.4 – 8.6g/kg humidity ratio. The average measured COP f was 1.6 (cold production divided by latent heat removed) for the range of conditions tested. The corresponding average COP sys of the system including the regenerator was 1.3 (cold production divided by heat input). The detailed operating parameters of each part of the test unit were also measured. The test data was compared with the simulated performance. The characteristic coefficients (such as the volumetric mass transfer coefficient of the air-water evaporative cooling module, etc.) in the mathematical model were modified to calibrate the model output to the measured data. The calibrated simulation model was used to investigate the control strategy of the fresh air processor. The flow rate of the strong solution into the unit and the number of operation stages may be controlled separately or together to meet different indoor air requirements at different outdoor conditions. The hot water driven liquid desiccant air conditioning system was compared with a typical vapor compression system with an average COP of 4.5; the pump and fan power of the proposed system was 40% of the combined chiller, pump, and fan consumption. We achieved savings of over 30% of the power consumption compared with the traditional system under the designed outdoor air conditions.

Xiaoyun Xie1?Yi Jiang1?Yidan Tang1?Xiaoqin Yi1?Shuanqiang Liu1
[1] Department of Building Science, Tsinghua University, Beijing, 100084, China

ivestock living environment and performance. These products are typically used on swine farms in the farrowing area to help “dry up” the newborn piglets to help “warm them up” more quickly, these desic-cants have been reported by producers to be effective in giving these little newborns a better chance to reach the mother sow and nurse.

KEN PALEN

ATLAS Copco has released the CD25-100 range of desiccant dryers including low pressure drop and reduced purge air consumption. The dryers have a large desiccant overfill, wide desiccant chambers, low air speed design and spring loading of the desiccant. Open cartridge design, wide connecting ports, and optimised flow have reduced the pressure drop to as little as 0.06 bars for smaller dryer’s.