Absorcare Desiccant

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.

For providing good performance of dehumidifier and regenerator with certain dimensions, a new type of internally cooled/heated dehumidifier/regenerator based on the plate-fin heat exchanger (PFHE) was designed. To investigate the behavior of the new equipment, an experimental setup was established in an environment chamber with regulable temperature and humidity air. By the internally cooled dehumidification testing, effects of the cooling water temperature, the air flow rate and the desiccant temperature on the dehumidification performance and the cooling efficiency were presented. The behavior of internally cooled dehumidification process was compared with that of the adiabatic dehumidification process. The results suggested that the cooling efficiency decreased with the increasing of the cooling water temperature and desiccant with low temperature could bring more mass transfer coefficients. There is an optimal air flow rate to achieve the maximum absolute humidity decrease of the air. By the internally heated regeneration testing, effects of the air flow rate and the desiccant inlet temperature on the regeneration performance and air outlet parameters were discussed and also compared with those of the adiabatic regeneration process. It was concluded that the regeneration efficiency of internally heated regeneration was more than that of the adiabatic regeneration, and the internally heated regenerator could offer better thermal performance.

Yonggao Yin?Xiaosong Zhang?Geng Wang?Lei Luo

Enthalpy and desiccant wheels are often used in commercial and industrial applications for energy recovery and air dehumidification operations, respectively. The modeling of these hygroscopic rotors is of great relevance either for manufacturer product optimization or for hourly simulations, when integrated in air treatment installations. Some simplified numerical methods have been proposed to predict the behavior of hygroscopic rotors, most of them assuming negligible internal resistances to heat and mass transfer and/or constant properties of the desiccant wall. In this article, a one-dimensional physical model is used to numerically investigate the behavior of an element of a porous desiccant wall that is assumed to belong to a hygroscopic wheel, and is submitted to an adsorption/desorption cyclic operation. The mathematical model is based on the solution of the differential equations of mass and energy conservation inside the porous medium. Moreover, the model was developed to treat the coupled heat and mass transfer phenomena in a detailed way, taking into account specified convective boundary conditions and considering the local and time changes of the medium properties during the sorption processes. The corresponding numerical model is used to perform simulations considering two distinct values of the wall thickness and different durations of the adsorption/desorption cycle. The results lead to a good understanding of the relationship between the characteristics of the sorption processes and the behavior of hygroscopic wheels, and provide guidelines for the wheel optimization, namely of the adsorption/desorption partition of the wheel frontal area.

Ruivo, CR?Costa, JJ?Figueiredo, AR
Univ Algarve, Escola Super Tecnol, AD Eng Mec, P-8005139 Faro, Portugal; Univ Coimbra, ADAI, Dept Mech Engn, Coimbra, Portugal

A solar-regenerated liquid desiccant ventilation pre-conditioning system has been proposed for use in hot and humid climates. The system aims to dehumidify the ventilation air which is the major source of latent load. A heat exchanger is used to cool the dehumidified air instead of typical evaporative cooling to maintain the dryness of the air. The use of solar energy at the regeneration process and cooling water from a cooling tower makes the system more passive. The simulation procedure for the proposed system has been presented. By inputting the climatic data and the physical parameters of all equipments, the operating parameters at each equipment and the performance parameters of the system can be evaluated. The simulation procedure is demonstrated by showing the daily profiles of the operating and performance parameters on a typical day as well as investigating the influence of the selected operating parameters on the system performance. The results suggest that the most influential parameters are solar radiation, ventilation rate, and desiccant solution concentration. The balance between the water removed at the dehumidifier and that evaporated at the regenerator needs to be considered to maintain uniform performance during continuous operation.

Thosapon Katejanekarn?S. Kumar
School of Environment, Resources and Development, Asian Institute of Technology, P.O. Box 4, Klong Luang, Pathumthani 12120, Thailand