Conventional Drying Research Articles

Experimental analysis on Solar Drying of Tomatoes and Cucumbers using PV/T Hybrid Solar Air Dryer

Drying is a method for removing moisture from food that is frequently used for storage and preservation. The most important goods in the agriculture industry are fruits and vegetables. Because of its extremely high nutritional value, it needs to be kept. The best way to maintain a food's nutritional worth is to keep it fresh. There are numerous ways to preserve this food, but nut drying is the most popular because it lengthens the item's shelf life. These items can contain up to and sometimes even more than 90% moisture. The key contributing factor to the proliferation of microorganisms that cause putrefaction is thought to be water content. This study compares the effectiveness of solar drying versus sun drying for drying fruits and vegetables. Rate of drying, weight. The experiments were carried out on tomatoes and cucumbers. The collector is inclined at 45° with horizontal and oriented in South – North direction with drying time of 5 hrs per day. During experimentation 5 temperatures, absolute humidity, air velocity and solar intensity were measured hourly in the month of March and April, 2023 for drying of tomatoes and cucumber slices. The hot air was transferred through the pipes to the chamber to dry the tomatoes and cucumber slices. The drying of tomatoes and cucumbers are reached around 90% with half of the time compared to conventional drying.

Evaluation of green banana pulp drying using infrared radiation with temperature control

The green banana flour (GBF) is a functional food rich in resistant starch and nutrients, probiotic, and has low glycemic index. The obtaining of the flour is usually done in dryers with high energy consumption, and possible deteriorating processes. These problems can be minimized with an adaptive temperature control system in infrared heat sources. The aim of this research was to quantify the energy savings in the production of green banana flour produced by infrared drying compared to the conventional process of drying in a resistance oven. The production of flour from green banana pulp was evaluated using an infrared radiation dryer with fruit surface temperature control (IR-FSTC). The IR-FSTC was performed by keeping the pulp surface at 50 °C and 60 °C. The results were compared with conventional drying using a resistive source. The energy consumption of drying using IR-FSTC was significantly reduced compared to the drying by resistive source and prevented the formation of hotspots. The drying process was also evaluated by physicochemical and spectroscopic analyses of the GBF. The product maintained the pH, titratable acidity, total soluble solids, and lipid content with values similar to those obtained by conventional heating oven drying. In turn, the spectroscopic analyses confirmed the maintenance of biomolecules inherent in GBF. Thus, it is concluded that the results contribute to the sustainable use of energy resources in the production of GBF.

Dewatering Spent Ion-Exchange Resins with Supercritical CO2

ABSTRACT A process for dewatering spent ion exchange resins (gel and porous) used in nuclear power plants by supercritical CO2 (sCO2) is described. The amount of water removed by sCO2 is much higher than that expected from solubility considerations alone. Water from gel-type resins is both dissolved by and emulsified in sCO2. Emulsification also occurs in the absence of solids when water alone is contacted by sCO2. It is not a factor for microporous resins where an additional mechanism, viscous fingering, is involved. It appears that bulk water is emulsifiable but not if it is held in pores. Dewatering via viscous fingering has been previously invoked for matrices such as wood and sludge. The resins can be dewatered and dried with sequential batches of sCO2 at sub-boiling temperatures. The CO2 can then be potentially reused after expansion and separation from the entrained water. Partial decompression of the water-laden sCO2 would lead to cooling, which would drop the water solubility substantially. A reduction of temperature from 90 oC to 65oC reduces the solubility of water in sCO2 by a factor of five. The condensed water could then be separated with a hydrocyclone. The footprint of sCO2 is much smaller than the conventional drying process. The energy costs are also much lower because evaporation of water is avoided.

Microwave vacuum and conventional drying characteristics of round Dendrocalamus asper

Drying round bamboo is important to ensure its dimensional stability, to protect it from biological agents and for making high quality products. Conventional kiln drying of bamboo requires extended drying periods. Microwave drying of bamboo has been studied recently and has been reported to be a very fast method of drying. Dendrocalamus asper (Schult. & Schult.f.) Backer is an important, large-sized bamboo, preferred for structural purposes and handicrafts manufacturing. However, it also shows a propensity to develop defects such as cracks during drying. In this study, eight culms of mature D. asper (about 3–3.5 years old) were felled and cut into two halves: upper half and lower half. Both parts were then cut into 900 mm long sections. Twenty sections each from the upper half were dried in a conventional kiln (CKD) at 50 °C and 70% RH; and another 20 sections from the upper half were subjected to microwave-vacuum drying (MWVD) at bamboo wall temperature 60–70 °C and 150 mbar pressure. Similarly, twenty sections each from the lower half bamboo sections were dried using CKD (50 °C, 70% RH), MWVD (bamboo wall at 60–80 °C, 150 mbar) and combination drying in which bamboo sections were first dried in CKD until the moisture content (MC%) dropped to below 30% (26%) and thereafter, further dried using MWVD. The time taken to dry the sections, MC% drop rate, defects, and energy consumption were analysed. MWVD took 12 h (upper half) to 20 h (bottom half) to dry the bamboo sections, whereas CKD took 12–15 days. Combination drying did not offer any major advantages. A lower number of defects were found in MWVD sections compared sections dried by CKD. On average, 3.78 units of electrical energy were consumed for the removal of 1 kg of water from bamboo during MWVD.

Experimental analysis of convective drying of paper and board

Conventional multi-cylinder drying of paper and board involves a mixture of conductive drying from steam-heated dryer cylinders and convective drying by the flow of heated air over the surface of the paper web in the pockets. Pocket ventilation is a critical component in assisting heat and mass transfer during the drying process but is the primary contributor toward removing evaporated water from the web. Air temperature, velocity, and humidity are critical parameters involved in the convective drying process. This paper covers an experimental study involving the design and development of a small lab-scale setup for convective drying of various grades of paper and board, monitoring multiple parameters like paper temperature, moisture content, air humidity, temperature, and velocity measured in situ as the drying proceeds with continuous and accurate sampling capabilities for all parameters in the sample and the system. Instantaneous drying rates, heat, and mass transfer coefficients were also deduced for every time step till the paper completely dried. Furthermore, the coefficients obtained were also reported in the form of dimensionless correlations, and the results were compared against traditional correlations used in the modeling of paper drying. This data will be useful in process development, modeling, design, and the paper drying process simulation.

Study on coarse-grained coal water removal characteristics via steam flash drying for low-rank coal upgrading

Low-rank coal drying plays a crucial role in achieving clean and efficient coal utilization. This study introduces steam flash drying, a novel method specifically designed for upgrading low-rank coal. Unlike conventional drying techniques, steam flash drying utilizes steam as the heat medium, generating a certain amount of condensation. This paper presents a comprehensive analysis of the calculated condensate quantity and the experimental measurement of coal particles' water-holding capacity to determine the initial moisture content before drying. Furthermore, the study investigates the steam flash drying effect on different-sized coal particles at a temperature of 497 K. The findings demonstrate that particles above 3 mm have lower water-holding capacity. The initial moisture content is determined by the particles' water-holding capacity and the combined raw coal water content and condensate content. The research reveals a diminishing flash-drying effect with increasing particle size, characterized by a rapid decrease followed by a gradual decline, observed at a critical point of 6 mm. By strategically adjusting the particle size distribution and employing mixing techniques, the coal drying effect can be significantly enhanced by 22%, ultimately leading to a remarkable 17% increase in processing capacity per unit volume. As a result, this study provides a theoretical foundation and optimization strategies for the clean and efficient utilization of coal through steam flash drying.

Microwave-infrared drying of cannabis (Cannabis sativa L.): Effect on drying characteristics, energy consumption and quality

Conventional cannabis drying is time-consuming and energy intensive. A quick and dependable drying of cannabis is essential to ensure high-quality products to meet increasing demands. This study explored a combined microwave and infrared (MI) drying on cannabis comparing with control environmental (CE) drying. MI was very efficient with a short drying time of 16–200 min, high moisture diffusivity of 7.95×10−09-8.70×10−08 m2/s, and low energy consumption of 390.49–1611.42 kJ. The Page and Modified Page drying models fitted well to describe and predict the MI drying characteristics of cannabis. Microstructural images identified shrinkage in glandular trichomes of cannabis, whereas colorimetric assessment resulted in alteration of color attributes due to MI drying. It also facilitated the conversion of acidic cannabinoids to their neutral forms by decreasing tetrahydrocannabinolic acid (THCA) in g/g of dry matter from 20.15% to 7.57% and increasing tetrahydrocannabinol (THC) from 6.31% to 16.65% that insignificantly (p≥0.05) affected the total THC level. MI drying resulted in a total terpenes concentration (%g/g of dry matters) of 0.541–0.730, insignificantly lower than CE drying (0.768). Overall, the study highlights MI as a rapid and energy-efficient drying for obtaining high quality cannabis, particularly for medicinal applications.

Study on free shrinkage and rheological characteristics of Eucalyptus urophylla ×E. grandis during conventional drying

ABSTRACT The collapse-prone nature of eucalyptus wood has implications for the measurement of drying rheological characteristics, particularly free shrinkage. The study outlined the calculation method for drying strain and the determination of drying stress direction. It also analyzed the free shrinkage properties of the wood, as well as the variations in elastic strain, viscoelastic strain, and mechano-sorptive creep strain throughout the drying process. The findings indicate the following: 1, there were no significant differences in free tangential shrinkage between the layers of the specimens. 2, the free tangential shrinkage of the layers was greater than that of the specimens. 3, the use of fresh thin wood that has not been subjected to drying stresses was recommended for accurate measurement of free shrinkage strains, as steaming does not fully reverse the plasticizing deformation caused by drying. 4, the collapse of eucalyptus wood in the early stages of drying hindered the reversal of tensile strain in elastic, viscoelastic, and mechano-sorptive behaviors.

Recent developments in tomato drying techniques: A comprehensive review

AbstractTomatoes, a highly perishable agricultural product, are commonly dried to extend their shelf life. They serve as raw materials in various domains, including direct consumption and as key ingredients in processed foods, functional foods, and nutraceuticals. However, producing dried tomato products with quality attributes equivalent to fresh tomatoes, such as nutrient content, appearance, flavor, texture, and reconstitution properties, poses significant challenges. Several research attempts have been made to evaluate the feasibility of different drying methods for tomatoes. Solar drying, hot air drying, and spray drying are commonly employed techniques, each with its own set of advantages and disadvantages. Conventional solar drying practices often result in extended drying times and undesirable quality parameters. Hence, it is imperative to adopt enhanced solar drying techniques for the large‐scale production of dried tomato products. Additionally, hybrid‐drying approaches can be explored to achieve better quality products with reduced drying times. Pretreatments before drying can also enhance overall drying performance. Combining conventional drying with novel drying methods, precise selection of drying parameters and pretreatments are demonstrated as efficient ways to improve the drying rate while preserving food quality. Modeling the drying process is also critical for designing large‐scale dryers, selecting appropriate drying conditions, maintaining product quality, and process optimization. Therefore, this article aims to provide detailed insight into existing drying methods with their unique features and modeling approaches, which may enable professionals and scientists to choose better and optimized tomato drying method to deliver the highest quality product to consumers.Practical ApplicationsProcessing tomatoes as dried products is a potential area to explore to minimize their postharvest loss. Lack of awareness regarding how to process, what parameters to consider, and which method to employ are hurdles in adopting and popularizing dried tomato products. Hence, it is crucial to consolidate the key findings pertaining to tomato drying from various methods into a unified platform. This will provide valuable guidance to future researchers and enable consumers to make informed decisions when selecting the most suitable drying method. Therefore, this comprehensive review aims to elucidate the current practices in tomato drying, highlighting their potential benefits and limitations.

Effects of different pretreatments on thin-layer drying kinetics, vitamin A retention and rehydration of orange-fleshed sweet potato slices

Orange-fleshed sweet potato (OFSP) is a bio-fortified sweet potato with a high beta-carotene content. OFSP deteriorates rapidly due to its high moisture content. Conventional air drying is one of the most common methods employed but has the disadvantage of low rates of moisture removal, hence the longer drying time, which affects the quality of the final product. Pretreatments prevent quality deterioration and hasten the drying rate. This study investigated the effects of different pretreatments on thin-layer drying kinetics and the quality of OFSP slices. Three-mm-thick OFSP slices were pretreated using three different pretreatments: lemon juice, salt solution, and hot water blanching (HWB). Pretreated slices were dried in a solar dryer. Data collection (weight, temperature, relative humidity, and solar radiation) was done at 1-hour intervals. Four mathematical models (Page, Logarithmic, Modified Page, and Henderson and Pabis) were fitted to the experimental data. Also, the quality parameters of vitamin A and rehydration were investigated. The dryer inside temperatures and relative humidity ranged from 26.93–44.53 oC and 36.87%–65.30%, respectively. The moisture content of fresh OFSP slices for both treated and untreated samples was found to be in the range of 291.55–302.24% (dry basis, db), which reduced to 25.25–35.25% (db) after drying. The drying time ranged between 11 and 13 hours. The page model was found to be the best model for untreated samples, with R2 of 0.9948, RMSE of 0.0151, and χ2 of 0.0097, while the logarithmic model best described the drying behaviour of all the pretreated samples because it had the highest values of R2 and the lowest values of RMSE and χ2. Lemon juice-pretreated samples had the best quality parameters (vitamin A retention and rehydration ratio). A maximum rehydration ratio of 1.6765 was obtained for samples pretreated with lemon juice, and a minimum rehydration ratio of 1.1390 was obtained from HWB-pretreted samples. The results, therefore, indicate that lemon juice can be used as a pretreatment for thin-layer drying of OFSP slices. Pretreatments help minimise postharvest losses associated with OFSP, thus contributing to solving food and nutrition insecurity challenges.

Nutritional and Functional Characterization of the Anchovy (Stolephorus indicus) Powder Produced by Conventional Drying and Foam Mat Drying

Anchovies (Stolephorus indicus) are abundant in both macro and micronutrients, including protein, carbohydrates, fat, and calcium. Their rich nutritive value has led to numerous applications in the food industry, particularly in fortifying food products for vulnerable groups. Proximate analysis is indispensable in the food industry for product development and quality control. The objectives of this study were to assess the proximate composition and functional properties of anchovy powder obtained through oven drying and foam mat drying. The characterization of anchovy powder encompassed functional properties, such as water solubility index, water absorption capacity, and physical parameters like colour and bulk density, as well as proximate chemical parameters. The results demonstrated that the protein content of anchovy powder obtained through oven drying was significantly higher than that from foam mat drying (p<0.05). The primary component of fish powders was protein (71.43±0.14%), followed by lipids (4.45±0.06%), ash (14.59±0.09%), moisture (8.55±0.01%), and carbohydrates (1.00±0.01%). Nevertheless, increasing the quantity of foaming agent did not enhance the solubility or water absorption capacity of the anchovy powder, despite the concurrent increase in its protein content.

Comprehensive Phytochemical and Antioxidant Analysis of Vitis Vinifera L. Seed and Peel: A Comparative Study of Conventional and Non-Conventional Drying Method

Comprehensive Phytochemical and Antioxidant Analysis of Vitis Vinifera L. Seed and Peel: A Comparative Study of Conventional and Non-Conventional Drying Method

An Paglara: A Solar-Powered Tikog Leaves Dryer Technology

Objectives: This study aims to introduce “A Paglara,” a pioneering solar-powered dryer meticulously crafted for the effective and sustainable drying of Tikog leaves. The process of developing “An Paglara” entailed the design, fabrication, and testing of the solar-powered dryer system. Key components include solar panels, an Arduino microcontroller, sensors for environmental monitoring, and a custom-designed drying chamber. Experimental trials conducted with “An Paglara” demonstrated remarkable results in expediting the drying time of Tikog leaves compared to traditional methods. The system achieved an average reduction of 30% in drying time while maintaining product quality and integrity. Moreover, “An Paglara” exhibited an energy efficiency improvement of 25% compared to conventional drying techniques. “An Paglara” stands out as an innovative solution for Tikog leaf drying, leveraging renewable solar energy and advanced control mechanisms to create optimal drying conditions. Its scalability and sustainability make it well-suited for small-scale artisanal production and community-based enterprises, contributing to rural development and environmental conservation efforts.

Enhancing the quality attributes of mint medicinal plant (Mentha spicata L.) through simultaneous combined ozone and infrared drying

AbstractMedicinal plants are widely used in various traditional and modern medical methods due to their therapeutic properties. Drying is a common method used to preserve the biochemical compounds of medicinal plants. Still, conventional drying methods can lead to the loss of active compounds due to exposure to high temperatures. This research aimed to design and construct an ozone generator for use in a combined dryer and evaluate the ozone, temperature, and hot air flow rate on the quality properties of mint (Mentha spicata L.). Drying experiments were conducted at varying temperatures, air flow speeds, and ozone levels. Results indicated that increasing temperature reduced total phenol and flavonoid content while increasing antioxidant capacity. Higher airflow speed positively influenced total phenol, total flavonoid content and antioxidant potency but reduced drying time. Ozone exposure increased total phenol, flavonoid content, antioxidant activity, and had minimal effect on drying time. Optimization revealed that a temperature of 52.47°C, air flow rate of 1.5 m/s, and 90.37% ozone concentration yielded favorable outcomes, including enhanced phenolic and flavonoid content, antioxidant power, and decreased energy consumption. Compared to other drying methods, the proposed ozone‐enhanced method proved superior in preserving bioactive compounds and maintaining a reasonable drying time. Overall, the research highlights the potential of ozone‐assisted drying for optimizing the quality of medicinal plants during preservation.Practical ApplicationThe paper introduces a novel and efficient method for preserving the quality of medicinal mint. By concurrently applying ozone and infrared drying techniques, this approach aims to capitalize on their synergistic effects in maintaining the plant's beneficial compounds. Ozone acts as a natural antimicrobial agent, preserving the plant's integrity, while infrared drying expedites the process without compromising the phytochemical profile. This innovative method not only ensures microbial safety and extended shelf life but also enhances the mint's aroma, flavor, and nutrient retention. The practical application of this combined technique holds promise for pharmaceutical and herbal industries, providing a valuable approach for optimizing the drying process and preserving the medicinal attributes of Mentha spicata L.

Pengeringan Kopi Robusta (Coffea canephora) Menggunakan Rumah Pengering Hybrid Tipe Rak

Coffee is one of the mainstay plantation commodities in Indonesia. In 2015 Indonesia had a coffee plantation area of 1,254,382 hectares, with a production of 379,005 tons. Coffee is one of the mainstay commodities in Indonesia's plantation sector. The role of coffee commodities for the Indonesian economy is quite important, both as a source of income for coffee farmers, a source of foreign exchange, a producer of industrial raw materials, and a provider of employment through processing, marketing, and trade activities (exports and imports). The Robusta coffee drying process will result in the dried product experiencing changes in color, texture, and aroma. The purpose of this study was to analyze the characteristics and drying process of Robusta coffee using a rack-type hybrid drying house with three treatments, namely, drying with a drying house using solar energy, drying with a drying house using solar energy and gas energy (hybrid) and conventional drying. The length of time to dry 10 kg of Robusta coffee to approximately 11.5% moisture content is for drying with a drying house using solar energy takes 96 hours or 12 days, for drying with a drying house using solar energy and gas (hybrid) takes 80 hours (10 days) and for drying using tampah (conventional) takes 104 hours (13 days). Keywords: Dryer, Hybrid, Robusta Coffee.

Quality evaluation of house cricket flour processed by electrohydrodynamic drying and pulsed electric fields treatment

House crickets are expected to play a significant role in the future food sector. Electrohydrodynamic (EHD) drying offers an environmentally friendly alternative to conventional drying methods. Pulsed electric fields (PEF) is a non-thermal process that facilitates conventional processes. EHD was applied to house crickets with and without PEF pretreatment, and the effect of PEF and EHD on the quality of the insects was evaluated. PEF pretreatment positively affected the oven drying at 60 °C by reducing its duration and thus decreasing the energy consumption by 14.22%. Moisture removal of EHD was not sufficient to replace oven drying, but when combined with oven drying, the overall energy consumption was reduced by >50%. PEF processing also increased the protein solubility (53.07% higher than the respective control) and antioxidant activity (24.05% higher than the respective control) of the oven-dried samples and reduced the histamine content of the EHD-dried samples (25.87% lower than the respective control).

Microwave Drying of Catalyst Layers for Fuel Cells and Electrolysers

Due to an increasing demand for sustainable energy, the polymer electrolyte membrane fuel cell (PEMFC) is considered a key technology in energy conversion with hydrogen as an energy carrier. The performance characteristics of a PEMFC is significantly influenced by the morphology of the catalyst layer[1], which is formed predominantly during the drying step in the manufacturing process.In order to improve the performance of PEMFC and hence reducing production costs, research effort as well as industrial interest has focused on the drying process. Moreover, energy efficiency of the drying step in the production of thin-film catalyst layers is considered a key driver of cost perspective for the mass-market introduction of PEM fuel cells and electrolyzers due to increasing energy costs and the need for reduction of environmental impact.In the presented work, an innovative drying approach for thin-film catalyst layers, used in PEMFC and electrolyzer applications, is investigated. The thin-film is either coated on a substrate and transferred onto a polymer electrolyte membrane in a second process step or is directly coated onto the polymer electrolyte membrane by doctor blade coating. Drying is performed by coupling of microwave radiation into the wet film, leading to a homogeneous and energy-efficient heating of the coated film. Energy losses of the microwave drying process are significantly reduced compared to conventional convective drying. Additionally, the microwave induced drying step offers maximum control during the process.Dried thin-films, produced in the lab scale, are transferred to a polymer electrolyte membrane by a hot-pressing step and are completed with gas diffusion layers to membrane electrode assemblies (MEA). Electrochemical performance of the MEA is characterized on a fuel cell test bench in single cell configuration. The morphology of the structure obtained from microwave drying is analyzed and compared to CCM samples dried in a conventional convective oven.The effect of a microwave-based drying process is discussed with regard to fuel cell performance and structure-property relations of the electrodes.

Simulation optimization and energy consumption evaluation on the wood solar drying kiln with heat storage and dehumidification system

The conventional wood drying process has high energy consumption and detrimental environmental impact. While solar energy has found widespread application in material drying, simulation software has been instrumental in optimizing drying processes and curbing energy consumption. Nevertheless, there remains a dearth of simulation and optimization studies specifically focusing on wood drying systems, particularly those incorporating phase-change heat storage devices.This study delves into the wood drying process in one year within a solar drying kiln equipped with a phase-change heat storage and dehumidification system. The investigation scrutinizes the impact of different operating parameters and heat storage devices on the temperature distribution across the entire system. Results indicate that through a new programming method, the simulation of the temperature change of the phase change thermal storage material is realized, and the visualization degree of the system is improved. The average relative error of simulated temperature and measured temperature is 2.29 %, which has a strong consistency. When dehumidifier air flow rate is 1500 m3/h, solar panel angle is 36°, the dehumidifier is turned off when the drying room temperature reaches 55 °C, and the dehumidifier is turned on when the drying room temperature drops below 55 °C, the highest energy efficiency can be achieved. Moreover, through simulation and optimization, the average indoor temperature increased by 24.05 %, and the system energy consumption reduced by about 56.23 %. This is equivalent to a reduction of 3,312.22 kg of CO2 emissions.In essence, this study provides a pathway for enterprises to realize tangible energy savings and emission reductions in the wood drying process, showcasing the potential of integrating solar energy, phase-change heat storage, and dehumidification for enhanced efficiency.

Comparative and comprehensive experimental analysis: Performance variation of a novel hybrid dryer

Conventional energy sources are integrated into solar dryers to allow them to operate day and night. Unlike previous applications, this work presents a novel hybrid dryer in which an external geothermal heat exchanger unit is integrated into an indirect solar dryer to overcome this problem. The tomato drying performance of the hybrid dryer was compared with a solar dryer and conventional shade drying in simple and ventilated modes. The proposed dryer's energy, exergy, and economic performance were evaluated using solar and geothermal energy. During the same period, the hybrid dryer reduced the samples to at least 3.64 times lower moisture content in simple mode than other dryers. In ventilated mode, this value was 2.97 times. Integration of ventilation into the hybrid dryer reduced average drying time from 64 to 56 h, specific moisture extraction rate from 0.63 to 0.60 kg/kWh, specific energy consumption from 3.94 to 2.78 kWh/kg, and payback time from 0.22 to 0.17 years. However, it increased the thermal and exergy efficiency of both dryers' solar air collectors by over 30 % and 27 %, respectively. As a result, the hybrid dryer continued the drying process even when there was no sun and achieved a significant advantage in drying tomatoes compared to the other two drying types. The proposed system will make locations where geothermal energy is available attractive for food drying.

Mechanistic modeling and analysis of thermal radiation in conventional, microwave-assisted, and hybrid freeze drying for biopharmaceutical manufacturing

In freeze drying, thermal radiation has a significant effect on the drying process of vials located near the corner and edge of the trays, resulting in non-uniformity of the products. Understanding and being able to predict the impact of thermal radiation are therefore critical to accurate determination of the drying process endpoint given the variation in heat transfer of each vial. This article presents a new mechanistic model that describes complex thermal radiation during primary drying in conventional, microwave-assisted, and hybrid freeze drying. Modeling of thermal radiation employs the diffuse gray surface model and radiation network approach, which systematically and accurately incorporates simultaneous radiation exchange between every surface including the chamber wall and vials, allowing the framework to be seamlessly applied for analyzing various freeze-dryer designs. Model validation with data from the literature shows accurate prediction of the drying times for all vials, including inner, edge, and corner vials. The validated model is demonstrated for thermal radiation analysis and parametric studies to guide the design and optimization of freeze dryers.