Heating Retention Time Research Articles

Direct numerical simulation of contaminant removal in presence of underfloor air distribution system

Indoor contaminant removal over 0.5 ≤ FrT ≤ 5.0, 0.5 ≤ N ≤ 5.0, and 50 ≤ Re ≤ 500 was investigated numerically, wherein FrT refers to the Froude number, N refers to the buoyancy ratio, and Re refers to the Reynolds number. As demonstrated, the ventilation effectiveness increased with increasing contaminant source intensity and air supply intensity at a constant air temperature, indicating that increase the fresh air can effectively eliminate contaminants in this case. At high air supply temperatures, the heat retention time and contaminant transport was extremely short, and the fresh air induced by strong natural convection floating lift was rapidly discharged. Additioanlly, the air supply intensity had significant effects on contaminant removal. Quantification of the ventilation effectiveness under the combined effects of air supply intensity, air supply temperature and contaminant source intensity was determined based on the results of direct numerical simulations.

Mild hybrid energy dual-slope solar stills: Design and performance

The critical increase in the lack of available freshwater worldwide owing to different anthropogenic and natural causes has led mankind to seek serious solutions, such as the use of solar stills. This study shows the design and performance of a dual-slope solar still powered by a mild hybrid power supply system. Different power supply configurations were created for the solar still, and commercial phase change materials were incorporated into the prototype. The highest freshwater production rate in the active solar still (6.76 l/m2d) was obtained when power was supplied from the portable photovoltaic plant at the beginning of the test, with an associated cost per liter of produced water of 0.2218 USD. It was shown that phase change materials increased the heat retention time and optimized the energy supply in the solar still. However, their use did not result in lower freshwater production costs.

A study on Fe removal in aluminum scrap to make A356 aluminum alloy

The domestic demand for A356 raw material is increasing, so the price is often very high. The goal of this study is to sort the scrap, then reduce Fe from about 1 % to less than 0.15 %. The reducing Fe by Na2B4O7 to refine aluminum scrap has been conducted under laboratory conditions. The results showed that the iron reduction rate increased with the addition of Na2B4O7 and the heat retention time and obeyed the first-order exponential law. The addition of flux containing Na2B4O7 can reduce the iron content from 1% to less than 0.1% and reach an optimal rate of 77 %. The XRD, SEM and EDS analyzes of aluminum samples described the microstructure and morphology of the obtained aluminum products. This product is a good raw material for making Al alloy group A356.

Thermal management of catalytic converter with heat pipe embedded in thermal energy storage to reduce cold start emissions

ABSTRACT The Thermal Energy Storage (TES) System aids in improving the cold start efficiency of the catalytic converter (CC). To further improve the TES and CC performance, loop heat pipes embedded into the PCM, TES unit are presented. For evaluation, three cases are considered: Case 1; CC without TES, Case 2; CC with TES, Case 3; CC with a heat pipe embedded in PCM TES. Mg70Zn24.9Al5.1 is used as PCM and paraffin oil as the working fluid for the heat pipe. Three 30 minute transient cycles with idle events in between were run, with the engine soaking for 30 minutes at ambient conditions with varied loads (0 to 100%) at 2000 rpm. Heat storage and release cycles were run for each load condition. Average warm-up HC, NOx and CO conversion efficiency improvement of 45–85% with Case 3, 35–62% with Case 2 compared to Case 1 were observed. Heat storage time was observed to be lower by ~ 35% for Case 3 while the heat retention time was observed to be better for Case 2 by ~44%. System efficiency and effectiveness were found to be better up to 14% and ~0.2 with Case 3 compared to Case 2. Overall Case 3 showed better performance with some penalty on the heat retention time compared Case 2.

Enhancement of catalytic converter performance to reduce cold start emissions with thermal energy storage – An experimental study

A “Thermal Energy Storage” (TES) system can assist in solving the cold start emission problem associated with the catalytic converter. “Phase change materials” (PCMs) can be used in the TES system to absorb heat from the exhaust gases, liquefy it and store it as latent heat. This makes it possible to store the exhaust heat during the engine running conditions and to release it on the catalyst substrate during the off-engine and low temperature start. A catalytic converter is integrated with a TES unit with Mg70Zn24.9Al5.1 as PCM having melting point in range of 310 °C & 157 kJ/kg as heat of fusion. This paper presents Experimental investigation of Catalytic Converter for exhaust temperature, conversion efficiency with and without TES unit. The investigation includes the heat storage and retention time during engine operation. Test cycle of 150 min with each load were run including idle events in between at 2000 rpm for different load conditions. Results showcased maximum average conversion efficiency improvement for 60 %, 53 % and 30 % for HC, NOx and CO respectively at No load condition during cold start. Heat Retention time was found higher for high loads, 100 % & 75 % load temperature was observed to remain above 100 0C for nearly 350 min.

Mechanical Properties of Eco-Friendly and Energy-Saving Mortar with Porous Feldspar

ABSTRACTPorous feldspar is a silicate mineral that is made up of more than 80% of SiO2 and Al2O3 as components. It has a large specific surface area than sand. It has an excellent reactivity with cement as a pozzolanic component. A normal mortar as a construction material is composed of 75% of sand and 25% of cement. Carbon dioxide (CO2) is a cause of environmental pollution. It is often made when making cement contained in mortar. Therefore, it is necessary to study alternative materials that can reduce the amount of cement used. This study was conducted using feldspar as a fine aggregate instead of sand. First, feldspar was standardized through physical testing. Compressive strength tests were then carried out to compare feldspar mortar and sand-based mortar. Hydration products of mortars were confirmed using a scanning electron microscope (SEM). Result of these tests revealed that when feldspar was used, the compressive strength tended to be high. In this study, Case 3 consisting of feldspar 80% and cement 20% with reduced use of cement was found to be the most suitable one. Secondly, to confirm the appropriateness of using feldspar mortars as a floor material, thermal conductivity and thermal efficiency experiments were conducted using mortars with ingredients that differed from a normal mortar. Results of these experiments revealed that feldspar mortar was more effective as an insulating material than a normal mortar because it had lower thermal conductivity and longer heat retention time than a normal mortar. Therefore, the use of feldspar mortar could have an energy reduction effect compared to a normal mortar as a flooring material in an ondol (under-heating) type floor-heating system in Korea.

Effect of Heat Retention Time and Pouring Temperature on Graphite Shape and Mechanical Properties of Gray Cast Iron

Effect of Heat Retention Time and Pouring Temperature on Graphite Shape and Mechanical Properties of Gray Cast Iron

Effect of Pyrolytic Temperature and Time on Characteristics of Typha angustifolia Derived Biochar and Preliminary Assessment of the Ecological Risk

A batch of biochar was produced from pyrolysis of Typha angustifolia (TBCs) at 200-500℃ for 2 h and 6 h to investigate the effects of pyrolytic temperature and heating retention time on the physico-chemical properties. Moreover, Escherichia coli (E. coli) HB101 and the seeds of Helianthus annuus were used to preliminarily test the ecological risk of the TBCs. Results showed that the heating retention time (i.e., 2 and 6 h) had no significant effect on the properties of TBCs, while pyrolytic temperature significantly affected TBCs' characteristics. As the pyrolysis temperature increased from 200 to 500℃, the mass yield and contents of hydrogen (H) and oxygen (O) decreased, while the contents of carbon (C) and ash increased. The pH and surface pores also increased with increasing pyrolytic temperature, whereas the O-containing functional group (e.g., -COOH and -OH) decreased. These results indicated the increased carbonization and aromatization of the TBCs. For the inherent nutrients of TBCs, the total phosphorus (TP) and available potassium (K) contents significantly increased as temperature increased. The main components of dissolved organic matter (DOM) of TBCs were humic acid-like and fulvic acid-like organic compounds. As the pyrolysis temperature increased, the content of humic acid-like organic compounds decreased, while the content of fulvic acid-like organic compounds increased. All the TBCs had no significant effect on the growth of E. coli HB101 and the seed germination of Helianthus annuus, indicating the little ecological risk of TBCs under the experimental conditions. These findings provide an alternative way for resource utilization of waste wetland biomass and provide important theoretical data for screening biochar in soil reclamation.

FRI0227 A USABILITY SURVEY OF WRIST MOUNTED DISPOSABLE HEAT PAD ON RAYNAUD’S PHENOMENON IN PATIENTS WITH CONNECTIVE TISSUE DISEASES

Background:For patients with connective tissue diseases (CTD), vasodilators are used to treat Raynaud’s phenomenon (RP), they are difficult to control only by medication. Although physicians recommend the use of a portable handwarmer or gloves to patients with CTD presenting with RP, sustained heat-retention effects cannot be obtained from them because the patients’ daily life-related activities prevent their continued use. Since the wrist mounted disposable heat pad maintains the degrees of freedom of the hands and fingers and can remain usable during the daily activities, we considered this heat pad as a useful and highly practical heating method for CTD patients presenting with RP.Objectives:To investigate the usability and changes in symptoms resulting from the use of the wrist mounted disposable heat pad in CTD patients presenting with RP.Methods:Subjects were 23 outpatients with CTD presenting with RP (23 females; mean age 62.6 years; mean duration following the onset of RP 10.3 years; 12 systemic sclerosis, 5 mixed connective tissue disease, 5 Sjögren’s syndrome, and 1 systemic lupus erythematosus) who had used the wrist mounted disposable heat pad (put the pad in a specifically designed holder and wrap it around wrist joint (max. temperature 42 degrees Celsius, heat-retention time 6 hours)). We investigated through interviews with them the use situations, usability, and changes in RP. During their using the heat pad, medication and daily life-related precautions against RP continued to be implemented as before.Results:Many patients had no knowledge of the heat pad (n=17, 73.9%). The most common wearing time of the heat pad was 5–6 hours (n=8, 34.8%). As for scenes of wearing the heat pad, patients who wore the pad when being out of the home accounted for the highest proportion (n=16, 69.6%), and as follows: at home (n=6, 26.1%), during kitchen work (n=3, 13.0%), and during housework (n=2, 8.7%). 17 patients (73.9%) replied that usability was “good”, and 18 (78.3%) replied that usability was “better” compared with conventional measures. Moreover, many patients (n=16, 69.6%) replied that RP and associated symptoms had become reduced or alleviated. No patients replied that RP and associated symptoms had become exacerbated or severer. In terms of advantages of using the heat pad, patients who replied that the site on which the pad was mounted was felt to be warm accounted for the highest proportion (n=8, 34.8%), and those who replied that sites other than where the pad was mounted (such as fingertips, hands, and arms) were also warmed accounted for virtually the same proportion (n=7, 30.4%). Over 60% of the patients (n=14, 60.9%) replied that symptoms associated with RP (skin color, cold sensation, and pain) had become reduced or disappeared. In terms of disadvantages of using the heat pad, patients who replied that it was bothersome to use the pad accounted for the highest proportion while other patients made replies referring to cost and bad appearance. No significant accident occurred and as many as 17 patients (73.9%) replied that they would like to continue to use the heat pad in the future.Conclusion:There have been few reports evaluating the usefulness of a heat pad for RP. The wrist mounted disposable heat pad was thought to be a heating method having the potential to achieve high levels of usability and practicality on CTD patients presenting with RP. Given that the heat pad alleviated RP or caused sites other than where the pad was mounted to be felt warm even though it did not directly heat the hands and fingers, the pad seemed to have usefulness attributed to the heating of the wrist. Although the heat pad seems to be an excellent method for addressing RP in patients’ daily lives, we hope that this heat pad will be evaluated on a larger number of patients with the addition of objective indices.

Heating and cooling capacity of phase change material coupled with screen mesh wick heat pipe for thermal energy storage applications

The thermal performance of a phase change material (PCM) heat pipe system is experimentally analysed using acetone as heat pipe fluid in a heat load range of 10-50 W at different flow rates of the condenser coolant. The evaporator of the heat pipe is enclosed in a chamber which filled with a PCM or water. Heat inputs are applied at the evaporator of the heat pipe through the PCM or water. In this study, the heat retention as well as cooling time of the PCM-water are estimated at different heat loads and flow rates of condenser coolant. Similarly, the thermal resistance, evaporator and condenser heat transfer coefficients are also estimated at different heat loads. It is observed that the PCM takes more time during heating and cooling cycles to reach the steady-state temperatures and the temperature values reached during heating are also higher for PCM compared to water. The use of PCM enhances the thermal storage capacity and shows a maximum enhancement of 200% in heat retention time compared to water at 50 W. Moreover, a maximum enhancement of 63.6% is observed in the steady-state temperature of the PCM compared to water. Similarly thermal resistance, evaporator wall temperature and heat transfer coefficients of the heat pipe also vary for PCM and water. The experimental results indicate that PCM or water can be used in this combined system depending upon requirement of thermal storage or electronics cooling.

Thermal properties of some Egyptian kaolin pastes for pelotherapeutic applications: Influence of particle geometry on thermal dosage release

Abstract The present study aims to evaluate the potentiality of 7 selected structural highly ordered kaolinite-rich samples from Egyptian Carboniferous sedimentary deposits (located at Abu Zenima district, west central Sinai peninsula) to use them in medicinal semisolid formulations as peloids. The effect of particle geometry and kaolinite crystallite size are studied to check their influence on thermal dosage performance. The studied samples exhibit a variable mineralogy. Kaolinite is the main constituent (ranging from 81 to 94%), followed by quartz (up to 14%), lesser amounts of anatase and halite, and traces of hematite, magnetite, alunite and gypsum. The kaolinite order “Hinckley Index” varies from 1.28 to 1.50. 1:1 (w/w) kaolin mud pastes were prepared with purified water in Eppendorf tubes using a touch vibration vortex mixer for 2 min. The cooling kinetics of pastes were measured by using a differential scanning calorimetry equipment (Shimadzu DSC-50Q). Specific heats were calculated, following Cara et al. (2000). The granulometry and geometric surface area were measured by laser diffraction (Mastersizer 2000LF, Malvern Instruments) in the range 0.02 and 1500 μm. All analyzed samples showed a clear predominance of particles under 4 μm (ranging from 82 to 94%), with median size (D50) ranging from 0.93 to 1.35 μm. The heat retention time during cooling from 50 °C to 32 °C reached up to 30.82 min, oscillating around an average of 28.72 min, and the temperature corresponding to the minimal dosage time (T20) was not exceed below 34.7 °C. A good correlation (R2 = 0.875) was found between heat retention time and specific heats. There is no correlation between kaolinite content and thermal properties, but R2 values around 0.6 are found with granulometry (finer the particles, greater the heat retention time t32 and the specific heat). Even if sample H5 (Gabal Hazbar deposit) is not the richest in kaolinite, it exhibits the best thermal dosage performance, in accordance with the granulometry (D50 = 0.93 μm), and geometric surface area (3.73 m2/g).

Experimental Investigation of a Finned Pentaerythritol-based Heat Storage Unit for Solar Cooking at 150-200 ̊C

An experimental study on the charging and discharging performance of a finned thermal energy storage unit (TESu) that utilizes pentaerythritol (PE) as phase change material (PCM) was conducted. It is known that fins enhance the heat transfer within TESu, however, the optimum PCM to fin volume ratio for a particular application is usually unknown. Therefore, this work compares the charging and discharging performances of three rectangular TESu prototypes with 6, 12, and 21 PE to fin volume ratio (P/F) per prototype. The performance comparison was in terms of (1) charging rapidity, (2) heat retention effectiveness, (3) temperature distribution, and (4) the cooking power. It is found that for 6 ≤ P/F ≤21, charging rapidity decreases with PE/fins ratio. On the other hand, the PE/fin volume ratio of higher than P/F > 12 has great influence on heat retention effectiveness, temperature distribution in the TESu, and cooking power. Therefore, 6 < P/F <12 strikes a balance between charging rapidity and discharging performance (heat retention time, improved temperature field as well cooking power). However, generalization to TESu for cooking application pends extension of this work to other PCM operated TESu.

Experimental investigations on using phase change material for performance improvement of storage-enhanced heat recovery room air-conditioner

The use of SEHRAC (storage-enhanced heat recovery room air-conditioner) for space cooling and free water heating has been confirmed effective but its overall performance will unavoidably be affected by the associated increase in water temperature in the heat recovery water tank. Measures to enhance the heat storage capacity of the water tank will thus be beneficial to the overall performance of SEHRAC. But virtually none has been done to date. For achieving this objective, the use of PCM (phase change material) in the water tank was proposed in this study. A prototype SEHRAC integrated with an expanded graphite/paraffin composite PCM was designed and setup in a test facility for laboratory experiments. Two identical sets of experiments with and without the use of PCM (wPCM and woPCM scenarios) under a range of outdoor temperature conditions were conducted. It was found that the wPCM scenario, as compared to the woPCM scenario, the overall coefficient of performance was 6.9%–9.8% higher and the heat retention time of the tank water was 21.1% longer. The results confirmed that the performance of SEHRAC could be improved by the use of PCM.