Air Humidity Ratio Research Articles

Optimal Design of Constructal T-Shaped Fin Under Partially Wet Condition for Enhanced Thermal Performance: An Analytical Approach

In refrigeration and air conditioning systems, the fin surface may become dry, fully wet or partially wet depending upon the psychometric, thermo-physical and geometric parameters. The current work is intended to determine the length of the dry portion, temperature distribution, performance and optimum design parameters of a T-shaped fin under partially wet condition. Temperature dependent thermal conductivity of the fin material is taken and the humidity ratio of saturated air is considered to vary linearly with the corresponding fin surface temperature. Considering these the governing equation of T-shaped fin becomes nonlinear and it has been solved analytically by using Homotopy Perturbation Method. The point of separation between the dry and wet portions of a T-shaped fin may be located either in the stem or flange part and hence, two cases having different governing equations and boundary conditions are analyzed in the current study. For the optimization study, Lagrange multiplier technique is employed and the results are obtained by maximizing the heat transfer rate for a constant fin volume. Further, a comparative study is presented between insulated and convective fin tip conditions.

A novel optimal constructal fork-shaped fin array design to ascertain thermo-heightened performance under dehumidifying conditions

The current work deals with the design and analysis of an array of constructal fork-shaped fins attached to a circular tube and operating under fully wet condition. For the mass transport process, a linear relation is adopted between the humidity ratio of saturated air and the corresponding fin surface temperature. After obtaining temperature distribution analytically, a metaheuristic optimization technique is adopted to maximize the net heat transfer rate of the fin array and un-finned surface imposing certain constraints. The constraints are taken such that the radial space limitations, fin material limitations as well minimum fin gap considerations are taken into account. As the present problem involves a large number of design parameters as well as the interrelated constraints, Particle Swarm Optimization technique has been employed for determining the optimum condition. The proposed theoretical analysis has been performed for different operating conditions and the results have been compared with the corresponding rectangular fin array. From the analysis, it has been found that optimum fork–shaped fin array with two branches gives higher heat transfer rate than the corresponding optimum rectangular fin array. For a typical situation (fin volume 0.0005 m3, air relative humidity 70%, ambient temperature 30 °C, base temperature 5 °C, convective heat transfer coefficient 20Wm-2 K−1, fin material thermal conductivity 236 Wm-1 K−1 and minimum gap between fins 0.002 m), optimum fork-shaped array with two branches gives 59.58% higher heat transfer rate than that of the optimum rectangular fin array. In certain cases, though the difference in heat transfer rate between optimum fork–shaped fin array with two branches and the corresponding optimum rectangular fin array is small, but the total fin length for the former case is found to be lower and thus fork shaped fin array with two branches is a better option than the rectangular fin array. However, no benefit in terms of either higher optimum heat transfer rate or lower total fin length is obtained by increasing the number of branches of the fork shaped fins beyond two.

An inverse approach to solving zone air infiltration rate and people count using indoor environmental sensor data

Physics-based simulation of energy use in buildings is widely used in building design and performance rating, controls design and operations. However, various challenges exist in the modeling process. Model parameters such as people count and air infiltration rate are usually highly uncertain, yet they have significant impacts on the simulation accuracy. With the increasing availability and affordability of sensors and meters in buildings, a large amount of measured data has been collected including indoor environmental parameters, such as room air dry-bulb temperature, humidity ratio, and CO2 concentration levels. Fusing these sensor data with traditional energy modeling poses new opportunities to improve simulation accuracy. This study develops a set of physics-based inverse algorithms which can solve the highly uncertain and hard-to-measure building parameters such as zone-level people count and air infiltration rate. A simulation-based case study is conducted to verify the inverse algorithms implemented in EnergyPlus covering various sensor measurement scenarios and different modeling use cases. The developed inverse models can solve the zone people count and air infiltration at sub-hourly resolution using the measured zone air temperature, humidity and/or CO2 concentration given other easy-to-measure model parameters are known.

Multilayered artificial neural network for performance prediction of an adiabatic solar liquid desiccant dehumidifier

Abstract In this study, a multi-layered artificial neural network (ANN) algorithm was developed and trained to predict the performance of a solar powered liquid desiccant air conditioning (LDAC) system particularly the adiabatic packed tower dehumidifier using Lithium Bromide (LiBr) desiccant. A reinforced technique of supervised learning based on error correction principle rule coupled with perceptron convergence theorem was applied to create the algorithm. The parameters such as temperature, flow rates and humidity ratio of both air and desiccant fluid were fed as inputs to the ANN algorithm and their respective outputs used to determine dehumidifier effectiveness and moisture removal rate (MRR). The ANN model when subjected to validity tests using vapour pressure of LiBr desiccant solution at specific random temperatures and concentrations, gave astounding outcomes with precise estimation to R2 values of 0.9999 for all desiccant concentration levels. Due to the variation in solar radiation, the MRR and effectiveness fluctuated with the change in desiccant and air temperatures, giving maximum differences of 0.2 g/s and 1.8% respectively between the predicted and measured values depicting a perfect match. With respect to humidity ratio, MRR was accurately predicted by ANN algorithm with maximum difference of 3.4969% while the mean variation was −0.5957%. With respect to air temperature, the dehumidifier effectiveness was perfectly predicted by the ANN algorithm to an average accuracy of 0.53% and extreme positive deviation of 4.14%. The MRR was replicated to a mean variation of 0.013% and highest point difference of 0.08%. In all the above cases, the mean and maximum differences between the ANN model and experimental values were far below the allowable limit of ± 5%, hence the algorithm was deemed to be successful and could find use in air conditioning scenarios. The ANN algorithm’s capability and flexibility test of processing unforeseen inputs was accurate with negligible deviations and prospects of predicting the desiccant’s vapour pressure, dehumidifier effectiveness and MRR within all ranges of temperature and concentration which then eliminates the need for use of charts.

A Full-Solid-State Humidity Pump for Localized Humidity Control

Summary Humidity management is essential and widely needed in various fields. Traditional moisture removal technologies are mostly based on cooling condensation or desiccant dehumidification. These methods come with inherent defects of energy efficiency and are bulky and complex for small-space humidity-control applications. Here, we demonstrate a full-solid-state humidity pump using the advantages of commercial thermoelectric coolers and silica gel materials. Silica gel is coated on the surface of heat sinks to minimize contact thermal resistance between the material and heat source while maintaining enough heat and mass transfer area between the desiccant and the air. The humidity pump device exhibits 0.61 g W−1 h−1 humidity transfer efficiency, corresponding to a humidity transfer rate of 28.38 g h−1. The proposed device neither uses refrigerant nor introduces liquid water. It opens up the possibility of use in localized humidity control applications with higher efficiency and a wider ambient temperature range than traditional technologies.

Experimental and numerical investigation of a novel hybrid deep-dehumidification system using liquid desiccant

Desiccant-based hybrid air-conditioning systems have recently become popular owing to a reduction in their energy consumption. In addition to the dehumidification process, regeneration is a necessary process in a hybrid system, and in all previous studies the regenerator (REG) has been separated from the liquid desiccant dehumidifier (DEH), which implies the need for a complex duct configuration and a large equipment space. In the present study, a novel hybrid liquid desiccant–heat pump air-conditioning system combined with a cooling coil is proposed for deep dehumidification with a supply air humidity ratio of below 5 g/kg, where the REG, condensing DEH (cooling coil), and liquid desiccant DEH are cascaded. This system not only maintains the energy performance advantages of hybrid systems over conventional systems, it also simplifies the layout of the entire system and guarantees a compact system structure, particularly for buildings with an existing central air-conditioning–chilled-water system. Using the proposed system, a coefficient of system performance (COPsys) of 2.4–3.2 has been obtained experimentally with an supply air humidity ratio of 2.1–4.5 g/kg. Despite the compact system structure, when the air is processed from 30 °C and 20 g/kg to 4 °C and 3.6 g/kg, the proposed system achieves a superior COPsys of 3.3 with an improvement of 13.8% when compared with a conventional liquid desiccant dehumidification system.

Modeling, simulation, and optimization of a microalgae biomass drying process

The aim of the present work was to develop a transient mathematical model focused on microalgae biomass drying, considering two phases: solid (wet biomass) and gas (drying air). Mass and thermal energy balances were written for each phase producing a system of ordinary differential equations (ODE). The solution of the ODE set delivers the temperature and air humidity ratio and biomass profiles with respect to time. The numerical results were directly compared with temperature experimental measurements—for both phases—and with the biomass humidity content. Data from experiment 1 were used to carry out the mathematical model adjustment, whereas data from experiment 2 were used for the experimental validation of the model. The model was adjusted by proposing a new correlation for the mass transfer coefficient and by calibrating the heat transfer coefficient. The transient numerical results were in good quantitative and qualitative agreement with the experimental results, ie, within the experimental error bars. Then the experimentally validated mathematical model was utilized to optimize the following parameters: (i) the electric heater power ( ) and the dry air mass flow rate ( ) and (ii) the convection oven length to width ratio (L/W). The goal was to minimize system energy consumption (objective function). The optimization procedure was subject to the following physical constraints: (i) fixed convection oven total volume and (ii) fixed biomass and drying air contact surface area. For the oven original geometry, = 3.0 kW and = 9 g s−1 were numerically found for minimum energy consumption, so that 36.9% and 43.5% energy consumption decreases were obtained, respectively, in comparison with the measurements of experiment 1. Next, the numerical geometric optimization found (L/W)opt = 9, with and , which was capable to reach a 51.6% energy consumption reduction in comparison with the original system tested in experiment 1. The novelty of this work consists of the development and experimental validation of a physically based microalgae biomass drying mathematical model, ie, instead of using empirical correlations to predict the drying time and temperature profiles and then minimize system energy consumption. Therefore, the results show that it is reasonable to state that the model could be used to design, control, and optimize drying systems with configurations similar to the one analyzed in this study.

Theoretical performance analysis of silica gel and composite polymer desiccant coated heat exchangers based on a CFD approach

A solid-desiccant coated heat exchanger (DCHE) technology can be applied to many heat transfer/exchange systems such as air-conditioners, heat pumps, adsorption chillers, and atmospheric water harvesters. Although the existing mathematical models can sufficiently predict the performance of the DCHEs, they are inapplicable for designing a new DCHE as the heat and mass transport coefficients used are derived from pre-determined empirical correlations. Therefore, in this paper, we developed a new mathematical platform to simulate the simultaneous heat and mass transfer phenomena that occur during DCHEs’ dehumidification/regeneration processes. Unlike existing models, the current model considers fluid flow, temperature, and moisture distributions across different domains. The effectiveness of the model was established by validating the performance of silica gel and composite polymer coated heat exchangers under different cooling and hot water temperatures. The maximum discrepancies between the model predictions and experimental data for outlet air humidity ratio and temperature were ±14% and ±12% respectively. A parametric study was then conducted to investigate the effects of key characteristic properties and fin-tube configurations on dynamic performance of DCHE. The respective dehumidification performance of two tube-fin and annular-fin DCHE configurations was observed to record 7% and 40% improvement in moisture removal capacity over the single-fin tube configuration.

Validation of multitask artificial neural networks to model desiccant wheels activated at low temperature

Desiccant wheels (DW) could be a serious alternative to conventional dehumidification systems based on direct expansion units, which depend on electrical energy. The main objective of this work was to evaluate the use of multitask artificial neural networks (ANNs) as a modelling technique for DWs activated at low temperature with low computational load and good accuracy. Two different ANN models were developed to predict two output variables: outlet process air temperature and humidity ratio. The results show that a sigmoid unit neural network obtained 0.390 and 2.987 for MSE and SEP, respectively. These results outline the effective transfer mechanism of multitask ANNs to extract common features of multiple tasks, being useful for modelling a DW activated at low temperature. On the other hand, moisture removal capacity of the DW and its performance were analysed under several inlet air conditions, showing an increase under process air conditions close to saturation air.

Performance analysis of a variable-stage open absorption heat pump combined with a membrane absorber

Compared to conventional closed absorption cycles, the open absorption cycle has a greater potential in latent heat recovery from exhausted moist gas since it recovers latent heat by mass transfer instead of heat transfer. Existing open absorption cycles including single-effect and multi-stage cycles have limitations on the waste heat utilization. This paper suggests a novel variable-stage open absorption heat pump cycle which can work on a wide range of temperature and humidity of exhaust gas. A membrane contactor is also suggested to replace traditional direct-contact absorbers to integrate with the new cycle. The membrane contactor has a higher mass and heat transfer efficiency and a greater potential to avoid solution carryover. Thermodynamic model of the new cycle combined with the membrane absorber model is developed. Parametric analysis is carried out to evaluate the performance of the new cycle. Simulation results show that, under the analyzed conditions, the equivalent stage number of the new cycle varies from 4 to 1 while coefficient of performance increases approximately from 1.2 to 2 with the increase of generation temperature and air humidity ratio. It indicates that the new cycle can cover the working temperature or humidity ranges of at least four conventional absorption cycles, including single-stage, 1.5-stage, double-stage, triple-stage absorption cycles. The new cycle works on a much wider temperature and humidity ranges than conventional multi-stage cycles because the pressures of the low-pressure generator and absorber will adjust themselves to adapt to the variations of generation temperature and air humidity ratio. The self-adaption of the pressures of the low-pressure generator and absorber is realized by the control of the solution mass flow rate. During the evaluated working ranges, coefficient of performance of the new cycle increases by 5.9–28.2% compared to conventional multi-stage absorption cycles. Influences of the operating conditions on the absorption rate of the membrane absorber is also conducted and discussed.

Studying the performance of a liquid desiccant indirect evaporative cooling system

A liquid desiccant-indirect evaporative cooling (LD-IEC) system has been proposed. The design is able to dehumidify and cool the product air simultaneously in one unit. A computational model has been developed to determine the performance of the heat and mass transfer process. The validation of the model demonstrated good agreement with the experimental data to within 10%. The detailed air treatment process has been theoretically studied. The thermal performance of the LD-IEC has been evaluated. Simulation results showed that the outlet temperature and humidity ratio were influenced by the liquid desiccant film length, intake air temperature, and intake air humidity ratio. For a specific inlet temperature and humidity ratio condition, a desired outlet condition can be obtained by adjusting the length of the liquid desiccant film.

A field study on indoor environment quality of Chinese inpatient buildings in a hot and humid region

In this research, objective physical measurements and subjective questionnaire surveys are used to investigate the indoor environment quality of Chinese inpatient buildings. The relative humidity in the inpatient buildings reaches 65%–75% during summer, resulting in the regular appearance of microbial growth on indoor surfaces. The average outdoor air change rate measured through the CO2 concentration decay method in the sampled inpatient rooms is 1.1 h−1, which is 45% below the standard threshold. The CO2 concentration in over 99% of the functional spaces is below the threshold of 1000 ppm. However, the dissatisfaction rate of the air freshness is higher than 25%, owing to the characteristics of healthcare activities. Insufficient fresh air volume and high supply air humidity ratio of the outdoor air system result in the inadequate dehumidification capacity and the over-humid environment in the inpatient buildings. From the perspective of indoor TVOC and PM2.5 concentration, a hospitable IAQ is achieved in the inpatient buildings. In the nurse unit, the illumination levels in public areas, such as patient corridors and nurse stations, are inadequate. The average noise levels (A) in the inpatient rooms and nurse stations are 50.7 and 61.6 dB, respectively, which exceeds the Chinese standard. According to the subjective survey, the dissatisfaction rates of overall IEQ in the summer for patients and visitors are 7.9% and 10.4%, respectively, while for staff it is 34.8%. Statistical analysis reveals that the satisfaction levels of the patient with the IEQ are higher than that of the visitor and staff.

Experimental analysis of dehumidification performance of counter and cross-flow liquid desiccant dehumidifiers

In a liquid desiccant dehumidifier, the air-to-solution flow direction plays an important role in the dehumidification performance and the physical size of the dehumidifier tower. In this research, the dehumidification performance of counter-flow and cross-flow liquid desiccant dehumidifiers were compared via a series of experiments carried out in the environmental test chamber. To predict the dehumidification performance of both flow type dehumidifiers in various operating conditions, empirical models returning the dehumidification effectiveness and the enthalpy effectiveness, which were adopted as performance indices, were also derived based on the experimental data. From the sensitivity analysis conducted by using the proposed empirical correlations, it was observed that when the inlet air humidity ratio increased from 10.1 g/kg to 22.7 g/kg, the dehumidification effectiveness and enthalpy effectiveness of the counter-flow liquid desiccant dehumidifier increased from 51.2% to 82.4% and 40.2% to 72.5%, respectively. Meanwhile, both effectiveness values of the cross-flow dehumidifier increased from 62.3% to 63.4% and 46.3% to 55.0%, respectively. Likewise, when inlet solution temperature varied from 15.2 to 31.1 °C, the dehumidification effectiveness and enthalpy effectiveness of the counter-flow type dehumidifier decreased from 71.7 to 45.4% and 64.4 to 47.3%, respectively, while those of a cross-flow type dehumidifier decreased from 65.3 to 54.8% and 55.8 to 45.2%. Consequently, one may conclude that the cross-flow liquid desiccant dehumidifier would provide relatively stable dehumidification performance regardless of the changes in operating parameter, but the cross-flow dehumidifier may have limited dehumidification performance, especially at the lower desiccant solution temperature and in highly humid process air conditions.

Effect of Desiccant Solution Temperature on Regeneration Performance of a Cross-Flow Regenerator

The purpose of this study is to investigate the effect of the inlet solution temperature on the performance of an adiabatic cross-flow regenerator using a lithium chloride (LiCl) aqueous solution, and to propose the optimal inlet solution temperature when operating this type of regenerator. In the experimental tests, the inlet solution temperature range varied from 50 to 90°C. The tests were carried out at 10°C intervals while the other conditions remained constant. The measurement parameters for the test were the inlet air dry-bulb temperature and humidity ratio, outlet air dry-bulb temperature and humidity ratio, air volume flow, solution density, and inlet and outlet solution temperatures. The regeneration effectiveness and coefficient of performance (COP) were selected to assess the heat and mass transfer performance of the cross-flow regenerator. The most important finding of this research was to determine the optimal solution inlet temperature in the cross-flow regenerator with the LiCl aqueous solution considering both the regenerator performance and energy consumption. The test results show that the recommended inlet solution temperature is 60°C, considering both regeneration effectiveness and COP.

Application of heat pump combined two-stage desiccant wheel fresh air system of residential buildings in mixed climate zone

The building requires dehumidification for a long period of time in mixed climate zone of China. As a conventional method for dehumidification, vapor compression systems remove the water vapor by cooling the process air below dew point. This system consumes a lot of energy for reheating the air to meet the requirement of supply air temperature. A heat pump combined with two-stage desiccant wheel (TSDW&HP) is proposed as an air conditioning and dehumidification system in this study. The operation performance of proposed system applied in a hypothetical residence with 3 residents was investigated and simulated by using TRNSYS software. The operation modes of the system are discussed for different scenarios of season and outdoor air humidity ratio. In dehumidification season, fresh air deals with all of the latent load. In air conditioning season, fresh air deals with all of the moisture load with part of the cooling load. When evaporation temperature of HP is reduced and more moisture load is processed by evaporator in air conditioning season, there is a balance point between the performance of DWs and heat pump. The energy consumption of TSDW&HP fresh air system was compared with a conventional fresh air conditioner during dehumidification season and air conditioning season. It was found that the energy-saving potential of this system is 27.3% compared with conventional air conditioner.

Experimental and model based performance investigation of a solid desiccant wheel dehumidifier in subtropical climate

This paper presents real time performance analysis of a silica gel based desiccant wheel dehumidifier. Thermodynamic model is also validated through comparison under a wide range of operating conditions for subtropical climate conditions. Initially, a mathematical model is developed by using various set of equations for desiccant wheel dehumidifier in engineering equation solver. After-wards, a parametric analysis of the system is performed including various design and climate parameters such as: inlet air humidity ratio, inlet air temperature, regeneration inlet humidity ratio, regeneration temperature, and rotation speed of the wheel. Then, an experimental set-up of the system is established in Taxila Pakistan for the real-time performance assessment. The results revealed that the optimal rotation speed of desiccant wheel ranged from 15-17 rph. The maximum model based and experimental effectiveness is 0.45 and 0.43, respectively at re-generation temperature of 80°C. The maximum and minimum root mean square error values for effectiveness are 3.2% and 2.1%, respectively. Thus, the comparison between experimental and model results showed a good agreement.

Evaluation of the frost properties on a semipermeable membrane

The onset of the formation of frost on a semipermeable membrane, which allows both heat and moisture transfer through it, can be delayed, due to the moisture transfer through the membrane however, at severe conditions, frost formation cannot be avoided completely. In this paper, the formation of frost on a semipermeable membrane is evaluated both visually and quantitatively. The frost thickness and mass, and the area of the surface covered with frost are measured for a semipermeable membrane and compared with those on an impermeable plastic surface. Moreover, the effect of operating conditions (air humidity ratio, air mass flow rate, liquid desiccant temperature and salt concentration) on the properties of the accumulated frost, on the semipermeable membrane, are investigated. The results show a 30–60 min delay in frost deposition and also the formation of a thinner, lighter frost layer on the semipermeable membrane compared to the impermeable surface. Also, results show that increasing the moisture transfer through the semipermeable membrane, by decreasing the humidity ratio of the cold liquid desiccant, can lead to frost that is less thick; however, increasing the humidity ratio of the humid air leads to a higher rate of frost formation. Increasing the air mass flow rate or decreasing the surface temperature increases the thickness of the frost layer on the semipermeable membrane.

Study on the solidification characteristics of molten slag droplets cooled by mixed cooling medium

Numerical studies on molten slag droplets solidification behaviors in humid air were carried out by using the hybrid evaporation and solidification models. The numerical model was firstly validated by the experimental data in the literatures, and then solidification time, temperature distribution, and movement of phase change interface during the solidification process were analyzed. The effects of humidity ratio (content of atomized water), air inlet temperature and velocity, and droplet diameter on solidification behaviors of molten slag were discussed. Finally, a correlation for predicting the solidification time was proposed. The results show that, generally, the solidification time is decreasing by increasing the air inlet velocity and humidity ratio, or decreasing the droplet diameter and air inlet temperature. The solidification rates represent a trend of gradual decline during the solidification process due to the ever-increasing thickness of the solid slag region, and they are normally higher at the upwind side but relatively lower at the leeward side, resulting in an off-center solidification process of a slag droplet. The humidity ratio has significant effect on the cooling air temperature distributions, steeper temperature gradient is observed thanks to the evaporation process of the atomized water. The present work suggests that the operational conditions are: the humidity ratio within the range of 10%∼20%, the air inlet velocity is 1.0 m/s and the air inlet temperature is 303 K, respectively.

Enhancing COP of an air-cooled chiller with integrating a water mist system to its condenser: Investigating the effect of spray nozzle orientation

Air-cooled chillers are widely used for providing cooling in buildings in hot and humid climates. Using a water mist system in connection with the chiller condenser can enhance the chiller COP. This paper studies the effect of a water mist system on chiller COP in various orientations of the spray nozzle. Besides, a sensitivity analysis is performed for some parameters of the ambient air including air temperature, air humidity ratio, and air velocity. Simulations are performed by the commercial ANSYS Fluent 16.0 software based on the Eulerian-Lagrangian approach. The nozzle orientation angle is introduced as the angle between the spray nozzle axis and the entering air stream direction. The simulations are done for five values of the orientation angle, including 0°, 22.5°, 45°, 67.5°, and 90°. The results suggest that increasing the orientation angle is usually beneficial to the system performance such that the orientation angle of 90° yields the maximum percent increase of COP of 10.6. This event is justified by the reduced horizontal momentum of droplets and consequently the high residence time of them and also the extended cooling area in elevated orientation angles. However, with the orientation angle of 22.5°, the system faces a performance breakdown leading to only 5.9% increase of COP. The deteriorated performance of the system in the 22.5° orientation angle is perceived to be mainly due to the small cooling area coverage and the low residence time of the water droplets because the droplets are constrained to move in a high momentum plume region of a small cross-sectional area in the orientation angle of 22.5°. The sensitivity analysis suggests that the investigated parameters highly affect the extent of the chiller COP enhancement.

Experimental investigation and parametric studies on structured packing chamber based liquid desiccant dehumidification and regeneration systems

In this paper, an experimental investigation carried out for estimating the overall energy exchange between the liquid desiccant and the ambient air is presented. The influence of air humidity ratio on the performance of the liquid desiccant dehumidification/regeneration system is studied in detail. A correlation for humidity ratio difference between the process air inlet and exit of the packed chamber in terms of known operating parameters is developed for both dehumidification and regeneration systems. A two–dimensional thermal model is proposed for predicting the performance of the adiabatic counter – flow liquid desiccant dehumidifier/regenerator. The proposed model is validated with the experimental data and found accurate. Influences of air humidity ratio, L/G ratio and Lewis number on the latent heat ratio of both the dehumidification and the regeneration systems are analysed. Using Derringer's desirability function method, for a given range of operating parameters, optimal inlet condition for the maximum humidity ratio difference between the inlet and the exit of the dehumidification/regeneration system is obtained.