DRYING OF ZUCCHINI AND CARROT SLICES: INFLUENCE OF TISSUE STRUCTURE ON MASS TRANSFER PARAMETERS

The present work aimed mainly at investigating the influence of tissue structure on dehydration characteristics of zucchini and carrot. Microwave power levels of 100, 350, 550 and 750 W used to dehydrate the samples with thicknesses of 3, 5, 7 and 9 mm. The results showed that moisture removal from the slices occurred in a short accelerating period at the process beginning followed by a falling rate period. The moisture diffusivity increased with both increasing microwave power and the samples thickness where the average values for zucchini and carrot slices changed from 1.17×10-8 to 9.42×10-8 and from 0.73×10-8 to 5.51×10-8 m2 s-1, respectively. The average activation energy for zucchini and carrot slices varied in the range of 1.22–1.68 and 1.57–1.84 W g-1, respectively and decreased with increasing samples thickness.

Drying characteristics and prediction of best fitted drying model for coriander leaves

Drying experiments were conducted on coriander leaves as affected by drying methods (solar greenhouse drying and open sun drying), pretreatments (dipping in a solution of magnesium chloride + sodium bicarbonate + potassium metabisulphite, boiled water blanching containing sodium metabisulphite, and untreated), and loading densities (2.0, 2.5 and 3.0 kg/m2). Validity of three commonly used drying models were examined to predict the most suitable drying model for coriander leaves. The increased drying temperature under solar greenhouse dryer (42°C) increases the amount of moisture removal from the coriander leaves and reduces the drying time by increasing the drying rate as compared to open sun drying (29°C), at all the selected levels of pretreatments and loading densities. Chemically treated coriander leaves dehydrated under a solar greenhouse dryer required less drying time than other treated leaves and dried leaves. Nevertheless, drying methods and loading densities had significant effects, while treatment effects were marginal. It was found that reduction of moisture and moisture removal rate per unit time occurred mostly in the falling rate period except some accelerated removal of moisture at the beginning up to 150 minutes. Page's model was found most appropriate for drying coriander leaves among the selected models.

Experimental investigation of a novel metal-organic framework (MOF) based humidity pump under high humidity conditions

Latent heat load accounts for a significant proportion of air-conditioning energy consumption and particularly for specific environment in humid climates. Traditional vapor-compression refrigeration dehumidification faces the problem of refrigerant leakage, overcooling and complicated mechanical systems. Here, we report a novel humidity pump that uses semiconductor refrigeration and metal-organic frameworks (MOFs) as dehumidification method, which can efficiently transport moisture from a relatively ‘low-humidity’ space to a high-humidity one. The working principles of the humidity pump were introduced that the process air flows through the cold desiccant coated heat exchanger and then comes into direct contact with the MOF coatings to transfer heat and mass. The dehumidification performance of humidity pump was investigated in high humidity, and the dehumidification coefficient of performance (DCOP), dehumidification rate and moisture removal efficiency using MIL-100(Fe) coatings were calculated. The results indicated that the MOF humidity pump possesses excellent moisture transfer ability.

INFRARED DEHYDRATION OF BLANCHED QUINCE SLICES: STUDY ON PROCESS AND MASS TRANSFER CHARACTERISTICS

In the present work, moisture removal characteristics of quince slices in a convective tray dryer were studied. The blanched slices (with thicknesses of 3, 5 and 7 mm) were dried at drying temperatures of 50, 60 and 70 °C and air flow rates of 1, 1.5 and 2 m/s. The analytical model proposed by Dincer and Dost was used to determine the mass transfer parameters. The obtained Biot numbers (0.108‒0.293) revealed that both the internal and external resistance control the moisture diffusion within the samples. The moisture diffusivity and convective mass transfer coefficient were found to be in the ranges of 1.578×10-7‒7.331×10-7 m2/s and 2.040×10-5‒3.507×10-5 m/s, respectively. The activation energies for moisture diffusion and surface mass evaporation were determined to be in the ranges of 17.607 to 48.019 kJ/mol and 5.270 to 27.430 kJ/mol, respectively.

Experimental study on dehumidification performance of liquid desiccant system with aqueous HCO2K solution

The liquid desiccant systems are one of the promising technologies in dehumidification applications. The experimental study on dehumidification performance of a counter flow structured packing liquid desiccant system is done with Aqueous HCO2K as working fluid. The HCO2K solution at different mass flow rate of air and solution is tested. The airflow rate is varied from 0.187 kg/s to 0.272 kg/s and the solution flow rate is varied from 0.053 to 0.115 kg/s. The output parameters, specific moisture change, moisture removal rate, dehumidification effectiveness and latent heat removal capacity varied in following ranges 3-4.2 g/kg of dry air, 2.4-3.1 kg/h, 0.12-0.21 and 1.7-2.1 kW respectively. Particularly when air flow rate increases from 0.187 kg/s to 0.272 kg/s the moisture removal performance improves about 11% whereas when the solution flow rate increases from 0.055 to 0.115 kg/s, improvement in moisture removal performance about 20%. The results imply that increase in solution flow rate always have the positive impact on dehumidification performance. The increase in airflow rate has the negative impact on specific moisture removal and effectiveness, but the impact is positive in case of the moisture removal rate and latent heat removal capacity. The Overall results show a promising dehumidification performance and further improvement is possible by incorporating a cooling system.

Thermodynamic Analysis of a Hybrid System Coupled Cooling, Heating and Liquid Dehumidification Powered by Geothermal Energy

The utilization of geothermal energy is favorable for the improvement of energy efficiency. A hybrid system consisting of a seasonal heating and cooling cycle, an absorption refrigeration cycle and a liquid dehumidification cycle is proposed to meet dehumidification, space cooling and space heating demands. Geothermal energy is utilized effectively in a cascade approach. Six performance indicators, including humidity efficiency, enthalpy efficiency, moisture removal rate, coefficient of performance, cooling capacity, and heating capacity, are developed to analyze the proposed system. The effect of key design parameters in terms of desiccant concentration, air humidity, air temperature, refrigeration temperature and segment temperature on the performance indicators are investigated. The simulation results indicated that the increase of the desiccant concentration makes the enthalpy efficiency, the coefficient of performance, the moisture removal rate and the cooling capacity increase and makes the humidity efficiency decrease. With the increase of air humidity, the humidity efficiency and moisture removal rate for the segment temperatures from 100 to 130 °C are approximately invariant. The decreasing rates of the humidity efficiency and the moisture removal rate with the segment temperature of 140 °C increases respectively. Six indicators, except the cooling capacity and heating capacity, decrease with an increase of air temperature. The heating capacity decreases by 49.88% with the reinjection temperature increasing from 70 to 80 °C. This work proposed a potential system to utilize geothermal for the dehumidification, space cooling and space heating effectively.

Study and Analysis of Solar Cabinet Dryer on Passive Mode by Using Aluminium Foil, Solar Selective Black Carbon Material and Silica Sand (Concrete)

In this research work started to study of various article which is related to solar cabinet dryer. In many article do work repetition and some having different type of work analysis. There are work mostly to increase its efficiency, workability and moisture removal rate with changes in different parameters. Some of authors work passive mode solar cabinet dryer and some was work on active solar cabinet dryer. In this study observed that some of researcher use silica sand and metals particles. Every parameter have focused on different purpose of work. After the study of various articles analyze that use of mixture black carbon material and silica concrete as a storage material. That is important for increase moisture removal rate and drying rate. It will also enhance efficiency and workability of solar cabinet dryer. That will use in industry and winter oriented season in future aspects.

Performance Investigation of a Hollow Fiber Membrane-Based Desiccant Liquid Air Dehumidification System

The membrane-based desiccant liquid air dehumidification system is a promising technology for efficient humidity control in buildings. The use of a membrane module allows, among other things, for a compact design with a relatively large heat and mass transfer area and eliminates carryover of solution droplets. In this paper, a cross-flow, hollow-fiber membrane module was proposed for air dehumidification and regeneration of lithium chloride. A two-dimensional heat and mass transfer model for cross-flow in a membrane module used for air dehumidification and liquid desiccant regeneration was developed. The effectiveness, moisture removal rate and moisture removal rate were studied numerically and validated against experimental results. Based on the numerical simulations, the most favorable ranges of operating conditions were determined. It was found that the operating conditions significantly impact the dehumidification performance. The proposed dehumidifier maintains its performance in a wide range of inlet air humidity ratios. For dehumidification, the recommended temperature of the incoming solution was in the range of 14–18 °C, while for regeneration the solution range was 40–50 °C. The packing fraction was suggested in the range of 0.30–0.40. These results can help design membrane-based liquid dehumidification systems.

Experimental Studies on Natural Convection Open and Closed Solar Drying Using External Reflector

This work presents the experimental investigation on a solar food dryer equipped with external reflectors to enhance the rate of drying efficiency by removing the moisture content available in the anchovy fish. A comparison on conventional open solar drying is carried out to assess the parameters such as drying efficiency, moisture removal rate, and heat energy required for drying the anchovy fish using the modified solar dryer using natural convection technique. The physical examination results on the dried products proved that using modified solar dryer, the dried product are free from insects, dust. Also, it is found that the loss of colour from the product is minimum while compared to conventional open solar drying. The results showed that the thermal efficiency of dryer 1 and dryer 2 are comparatively higher as compared to that of conventional open solar drying and found as 16.73 and 19.34 % respectively.