NTU Value Research Articles

Entropy generation minimization for different types of heat exchangers using nanofluids

ABSTRACT In view of the current global energy situation, increasing the efficiency of heat exchangers can contribute significantly to reducing energy consumption and greenhouse gas emissions. In this study, the effects of nanofluids (SiO2/Water) prepared at different fluid flow rates and different volumetric concentrations (vol.%0.1-0.2-0.3) on three heat exchangers (Shell and Tube, Double Pipe, Plate) with the same capacity were investigated experimentally and statistically. It was concluded that there was an increase of 47% in effectiveness and 87.3% in NTU value with the increase in the volumetric concentrations of nanofluids and fluid flow rate. With the use of nanofluids, it was observed that entropy production decreased by up to 56.08%. The results obtained were analyzed using Response Surface Methodology (RSM) and mathematical models were created and the prediction capabilities of the models were 98% and above. Entropy minimization was performed using statistical methods and it was statistically determined that plate heat exchangers give better results among heat exchangers with the same capacity. It is concluded that the entropy production is minimum when the fluid flow rate is 2 lpm, the volumetric concentration is 0.3% and a plate heat exchanger is used. This study has provided a different and comprehensive perspective on heat exchangers, and it is thought that it will give many ideas to researchers working in this field.

Removal of turbidity from lake water using novel Chrysopogon zizanioides and Hemidesmus indicus

The primary objective of the research is to investigate the efficacy of the natural filtration process utilising the novel species Chrysopogon zizanioides and Hemidesmus indicus for turbidity reduction. The novel Chrysopogon zizanioides and Hemidesmus indicus serve as filter media for the purpose of eliminating turbidity in lake water. The features of the natural fibres were determined using SEM analysis, EDS analysis, and FTIR analysis. There are two groups being considered: group 1 consists of the unique Chrysopogon zizanioides, and group 2 consists of Hemidesmus indicus. There are 18 samples in each category. The sample size is N = 36. The pretest power is determined using a significance level of 0.05 and a confidence level of 95%, resulting in a power of 80%. The turbidity level of the lake water is 25.5 NTU. Upon completion of the process, the new Chrysopogon zizanioides demonstrates a turbidity removal percentage of 77.24%, while Hemidesmus indicus achieves a turbidity removal percentage of 80.23%. The statistical analysis conducted using SPSS yielded a significance level of 0.224 (P < 0.5). The average NTU values of groups 1 and 2 are 6.50 and 5.65 correspondingly. The standard deviation for the two cases is 4.36939 and 4.02502, respectively. Hemidesmus indicus is more effective at removing turbidity than Chrysopogon zizanioides.

SISTEM RESIRKULASI AIR OTOMATIS UNTUK PENGHEMATAN AIR BERSIH DAN ENERGI PADA BUDIDAYA IKAN NILA

The acidity and turbidity of water are essential factors in tilapia farming, so it is necessary to control the acidity (pH) and turbidity (NTU) of water. This research aims to develop an automatic water recirculation system to save the use of clean water and energy consumption in tilapia fish farming using a microcontroller based on pH and turbidity (NTU) values. The research method used is experimental, starting with design and manfacture an Experimental apparatus in the form of a fish pond from a box-shaped tarpaulin, a filter system, a water circulation system consisting of pipes and a pump that has a suction power of 25 lpm, an Arduino-based microcontroller water quality controller. Tests were carried out by comparing water's pH and NTU values before and after filtering. The results showed that using a water recirculation system in a fish pond equipped with a filter system and an Arduino-based microcontroller system can significantly maintain the pH value and reduce the turbidity level (NTU). Using a recirculation system provides energy savings for pump consumption of 51.4% at a water flow rate of 15 lpm and 32.3% at a water flow rate of 25 lpm compared to conventional systems. Overall, the recirculation system provides the benefits of energy savings in pump operation, savings in water usage, and controlled water quality.

Energy and exergy analysis of a liquid desiccant heat and mass transfer loop with natural convection: The effect of heat sink and heat source temperature

Desiccant systems, as a promising air conditioning technology have opened new aspects as a replacement for vapor compression systems. The liquid desiccant energy exchanger system with natural convection flow is proposed here; the system is a loop with two hollow fiber membrane air-desiccant exchanger of shell-and-tube type that works as the humidifier and regenerator. The LiCl aqueous solution as desiccant directed over the fibers and the air is inside the fibers; the water stream flows outside the modules to provide the required heat exchange. The heat sink and source as merged subparts of the exchangers have a major influence on system performance. The system is examined from the energetic and exergetic viewpoints at different heat sink and heat source temperatures. Keeping the fixed air flow rate and using the standard air properties, the cold and hot water temperatures of 15–25 °C and 50–70 were employed and the effectiveness coefficients including the latent, sensible and total and 2nd law efficiency evaluated. It was shown that the values of NTU and Cr* depend on each other and attenuating effect of NTU reduction is higher than enhancing effect of Cr* increase on effectiveness values. The prominent factor on exergy performance which hinders the effect of the other parameters is the solution flow rate. Also, the highest and lowest values of 2 nd law efficiency are 81% and 5% which are for temperature pairs of (52, 20) and (65,25), respectively.

Analisis Perpindahan Panas pada Sirkulasi Air Penyulingan Nilam dengan Tangki Bervolume 150 Liter

Analisis Perpindahan Panas pada Sirkulasi Air Penyulingan Nilam dengan Tangki Bervolume 150 Liter

Baseline water quality of the Gold Coast Broadwater, southern Moreton Bay (Australia).

This study establishes baseline water quality characteristics for the Gold Coast Broadwater, southern Moreton Bay (Australia) utilising routinely monitored parameters between 2016 and 2021, across 18 sites. Combined site mean concentrations of NOx-N, NH3-N and total nitrogen were 11.4±33.4μg/L, 12.7±27.2μg/L, and 169±109μg/L, respectively, whilst PO4-P and total phosphorous were 7.30±5.10μg/L and 21.7±14.1μg/L. Additionally, total suspended solids and turbidity combined site means were 6.6±6.0mg/L and 3.4±2.9 NTU, respectively. During high rainfall periods nutrient concentrations increased by up to >200-, >150-, 15-, 12- and >12-fold for NOx-N, NH3-N, TN, PO4-P and TP, respectively, compared to quiescent conditions. Furthermore, TSS and NTU values increased by up to 15- and 40-fold during periods of measured rainfall compared to quiescent conditions.

Influence of axial heat conduction in solid walls and fins on the overall thermal performance of an additively manufactured high-temperature heat exchanger

Due to the increasing use of high-temperature processes in mobile applications, the demand for compact and efficient high-temperature heat exchangers continues to rise. However, with increasingly reduced installation space, the parasitic effect of axial heat conduction in the wall material of the heat exchanger is also gaining considerable influence. In this manuscript, the influence of axial heat conduction in the wall and fin material on the thermal performance of an additively manufactured high temperature heat exchanger is to be examined. For this purpose, an analytical calculation model as well as the analytical solution method is presented and successfully validated by means of experimentally recorded measurement data of an additively manufactured heat exchanger, which was tested at temperatures up to 750 °C. Subsequently, the calculation programme is used to determine the influence of the axial heat conduction on the effectiveness as well as on the NTU value of an additively manufactured Plate-Fin heat exchanger. The results show a drop in the NTU value of up to 50% at balanced flow compared to the case without heat conduction, which reduces the effectiveness and thus the performance of the heat exchanger by up to 5.5%.

Turbidity characterization as a decision-making tool for extra virgin olive oil stability treatments

The extra virgin olive oil (EVOO) commercialized by olive oil companies usually has highly variable turbidity characteristics. Ten veiled EVOOs with different water content, insoluble solid content, water activity, degree of turbidity, and microbial cell count, and their respective filtered samples, were studied both to assess the risk of degradation phenomena and to suggest a rapid method to measure oil quality stability. The EVOO samples were analyzed for legal parameters, phenolic compounds, volatile organic compounds, and sensory attributes, immediately after purchase and after 45 and 180 days of storage at room temperature in dark conditions. A statistically significant relationship was found between water content and oil degradation during storage; hydrolytic phenomena and microbial spoilage occurred, causing variations in the oil quality in terms of phenolic compound hydrolysis, fusty and fruity sensory attributes, and volatile compound content. A > 0.2 %w/w water content value was measured as predicting a high risk of oil degradation. Moreover, since the research determined an original relationship between water content and NTU, we proposed that olive oil companies should adopt the following decision-making approach: EVOO with NTU values > 100–200 should be subjected to a schedule of treatments that reduce water content in a short time.

Analysis of Longitudinal Finned Pipes in Cross-Flow Heat Exchanger

In this case, the recovery of excess heat in the steel-making process becomes challenging to save energy effectively and efficiently. One way to help the process of heat recovery in the steel-making process is with a heat exchanger. This heat exchanger maximizes the production process work. However, in the application, the heat exchanger developed to date can still work optimally. Based on the literature study that has been done previously for the design of the heat exchanger, in this study, the addition of four longitudinal fins variations with the cross-flow flow was carried out. This research compares the heat exchanger performance finned pipes with pipes without fins design, where liquid and airflow rates are varied. This study evaluated whether the longitudinal fins configuration and the fluid flow rate affect the cross-flow heat exchanger performance. The results show that fins addition on the copper pipes increases the value of Nusselt number 2.56% in liquid fluid and 16.57% in air fluid and increases the NTU value of its effectiveness by 24.77%.

Assessment of fish species richness and physicochemical parameters of Mt. Hamiguitan Range Wildlife Sanctuary river systems in Mindanao, Philippines

Abstract. Dapar MLG, Lagumbay AJD, Parcon J, Tubongbanua Jr. RM, Amoroso VB. 2021. Assessment of fish species richness and physicochemical parameters of Mt. Hamiguitan Range Wildlife Sanctuary river systems in Mindanao, Philippines. Intl J Bonorowo Wetlands 11: 58-68. Being a UNESCO World Heritage Site, Mt. Hamiguitan Range Wildlife Sanctuary (MHRWS) is an exceptional area of diverse flora and fauna with conservation concerns. MHRWS river systems provide significant spawning and nursery grounds for freshwater fishes. However, anthropogenic activities may result in the degradation of fish habitats which calls for conservation. This study provides an updated assessment of the fish diversity of selected MHRWS river systems and recommends policies for the proper management of the rivers and riparian ecosystems. An inventory of fish species and an assessment of the physicochemical parameters were conducted in the three river systems of Mt. Hamiguitan Range Wildlife Sanctuary. A series of line transect of 100 m were established along the banks of the three rivers in three sampling stations (upstream, midstream, and downstream). Results showed that Dumagooc River has the highest number of fish species compared to Maug and Banahaw River. Generally, the species richness increased from upstream to downstream. The high species richness observed upstream and midstream is due to the presence of an intact forest with areas far from human disturbances. A total of 31 species in 11 families comprising 121 individuals were collected and identified. Of these, one endemic species, 29 native species and two introduced species were identified, representing 4.16% of 48 species recorded in the country. As to the physicochemical characteristics of the three river systems, the results showed that the temperature, pH, NTU and DO values of the sampling sites are within the minimum acceptable limit to be considered as within the standards for class AA, A, and B rivers.

Hyperplane games, prize games and NTU values

Hyperplane games, prize games and NTU values

Performance Analysis of a Printed Circuit Heat Exchanger with a Novel Mirror-Symmetric Channel Design

The printed circuit heat exchanger (PCHE) is a promising waste heat recovery technology to improve energy efficiency. The current investigation presents the experimental results on the thermal performance of a novel PCHE for low-temperature waste heat recovery. The novel PCHE was manufactured using precision machining and diffusion bonding. The thermal performances, such as effectiveness and NTU values at different temperatures, are evaluated, and water is used as a working fluid. The experimental results indicate that the PCHE’s effectiveness is around 0.979 for an inlet flow temperature of 95 °C. The predominant factors affecting the thermal performance of the PCHE are the inlet flow temperature and the flow rate of the working fluid. In addition, a comparison of the experimental results and the literature shows that the effectiveness of the PCHE is better than the others, which have fewer layers of PCHE fins.

Irritation Test and Effectiveness of The Clean Power Activated Charcoal Palm Shells (Elaeis guineensis Jacg) as Adsorbent Dirt on The Hair

The dirty and itchy scalp is very annoying in appearance, which is the onset of dandruff. Dandruff is due to the accumulation of dead skin cells, dry and oily scalp as well as the presence of skin infections and fungi in the head. To avoid the onset of dirt or dandruff to hair, it is necessary to do cleaning regularly using cosmetics one of them is active charcoal-based shampoo palm kernel shells. The capability of palm kernel shells can absorb dirt twice from commercial active charcoal to cleanse the skin to the fullest. This research aims to effectively absorption of the dirt in Invitro on the active charcoal shampoo of palm shells with a concentration of 12%. Invitro tests the effectiveness of the impurities absorbent by using a turbidimetry tool with a Nephelometric Turbidity Unit value or frequency number. While the irritation test is done on 10 people panelists. Comparative control used commercial shampoo as a positive control and base shampoo as a negative control. The results showed that a 12% palm shell activated charcoal shampoo provided an NTU value of 11,400 while a commercial shampoo gave an NTU value of 786. No panelists have irritation on the scalp. From the obtained results can be concluded that the active oil palm Shell Shampoo has the absorbent power to the dirt from a commercial shampoo and safe to use.

웨이비 패턴을 가진 판형 열교환기의 성능에 관한 연구

In terms of space-saving, the design of more compact heat exchangers is important. Also, to meet the demand for saving energy and resources today, manufacturers are trying to enhance efficiency and reduce the size and weight of heat exchangers. Over the past decades, there have been tremendous advancements in the manufacturing technology of high-efficiency heat exchangers. This has allowed the use of high-performance heat exchangers. Consequently, those heat exchangers have applied to almost all industries. When compared with the well-established shell & tube heat exchangers, plate heat exchangers show a lot of advantages like high NTU values, compactness, low cost, multi duties, and reduced fouling, etc. To get better thermal performances of plate heat exchangers, a new wavy patterned heat plate was developed through CFD analysis, and it then was experimentally tested to verify the validity of CFD and to compare with a plate heat exchanger with a conventional herringbone pattern. In this study, the development process is introduced, and the results are shared which wavy patterns are better than herringbone patterns.

Hyperplane Games, Prize Games and NTU Values

Hyperplane Games, Prize Games and NTU Values

A Comparison of NTU Values in a Cooperative Game with Incomplete Information

Several value-like solutions concepts are computed and compared in a cooperative game with incomplete information and non-transferable utility.

Performansi Alat Penukar Kalor Udara-Tanah (Earth-Air Heat Exchanger) dengan Siklus Terbuka di Kota Medan

The purpose of this study was to obtain the performance of an EAHE (earth air heat exchanger) with weather conditions in the Medan city. The research method carried out was experimental in the field for several days with varying weather conditions. The air conditioning system using an Air-Earth Heat exchanger has tested its performance by comparing the experimental results with the model of equations that have been developed by the previous researchers. The incoming air velocity 2 m/s is obtained by the output temperature on average for the results experiment with 27.1 o C and for theoretical results of 26.5 o C with an average air temperature of 32.1 o C. As for the incoming air velocity 3 m/s, the resulting output temperature averages for the experimental results of 27.3 o C and for theoretical results of 26.9 o C with an average air temperature that is 33.8 o C. The higher the air intake velocity, the higher the output temperature in the Air-Earth heat exchanger. At 2 m/s air velocity, the output temperature is 27.1 o C and then rises to 27.3 o C at air velocity enter 3 m/s. The effectiveness of the earth heat exchanger at the incoming air velocity 2 m/s for the experimental results was 0.84 while the theoretical calculation was 0.97. From the results of multiple regression analysis, it is found that the NTU and inlet air temperature values have a very strong relationship to the COP value. The correlation coefficient is 0.916 at a speed of 2 m/s and 0.959 at a speed of 3 m/s. The results show great potential for the development of ground-air heat exchangers as a passive cooling system building solution.

Effect of turbidity on water disinfection by chlorination with the emphasis on humic acids and chalk

ABSTRACTChlorine is globally the most widely used chemical for water disinfection. Whereas disinfection efficiency is well known to depend on water pH and temperature, the effect of turbidity is less well studied. Although turbidity is measured online in most drinking water works and most countries where regulations exist have set limits of <1 NTU for water leaving the works, the composition of turbidity is typically unknown. Given the heterogeneous nature of substances contributing to turbidity, the aim of this work was to study the effect of selected compounds on chlorination efficacy. The effect of humic acids and chalk on the inactivation of the indicator bacteria Escherichia coli and Enterococcus faecalis was assessed at neutral pH at different turbidity levels using both plate counting and flow cytometry in combination with membrane integrity staining. For humic acids, a turbidity of 1 NTU (corresponding to 2 mg L−1) was identified as a critical threshold, which when exceeded was found to have a negative impact on chlorine disinfection. Chalk, on the other hand, had no measurable impact up to 5 NTU. The observation applied to both bacterial species with identical conclusions from the two diagnostic methods. Results corroborate that different turbidity causing substances affect chlorination efficiency to very different extents with chlorine demand by organic material probably being the most important determinant. In the case of turbidities >1 NTU, turbidity measurement benefits from the consideration of the organic content as mere NTU values do not allow predicting an impact on chlorination efficiency.

On the Values of Bayesian Cooperative Games with Sidepayments

In this paper we explore the relationship between several value-like solution concepts for cooperative games with incomplete information and utility transfers in the form of sidepayments. In our model, state-contingent contracts are required to be incentive compatible, and thus utility might not be not fully transferable (as it would be in the complete information case). When we restrict our attention to games with orthogonal coalitions (i.e., which do not involve strategic externalities), our first main result states that Myerson’s [Cooperative games with incomplete information. Int. J. Game Theory. (1984), 13, 69-96] generalization of the Shapley NTU value and Salamanca’s [A generalization of the Harsanyi NTU value to games with incomplete information. (2016), HAL 01579898] extension of the Harsanyi NTU value are interim utility equivalent. If we allow for arbitrary informational and strategic externalities, our second main result establishes that the ex-ante evaluation of Myerson’s solution equals Kalai and Kalai’s [Cooperation in strategic games revisited. Q. J. Econ. (2013) 128, 917-966] cooperative-competitive value in two-player games with verifiable types.

Effect of ambient heat-in-leak on the performance of three-fluid cross-flow heat exchanger

PurposeHeat exchangers working in cryogenic temperature ranges are strongly affected by heat ingression from the ambient. This paper aims to investigate the effect of ambient heat-in-leak on the performance of a three-fluid cross-flow cryogenic heat exchanger.Design/methodology/approachThe governing equations are derived for a three-fluid cross-flow cryogenic heat exchanger based on the conservation of energy principle. For given fluid inlet temperatures, the governing equations are solved using the finite element method to obtain exit temperatures of the three-fluid exchanger. The performance of the heat exchanger is determined using effectiveness-number of transfer units (e-NTU) method. In the present analysis, the amount of ambient heat-in-leak to the heat exchanger is accounted by two parameters Ht and Hb. The variation of the heat exchanger effectiveness due to ambient heat-in-leak is analyzed for various non-dimensional parameters defined to study the heat exchanger performance.FindingsThe effect of ambient heat in leak to the heat exchanger from the surrounding is to increase the dimensionless exit mean temperature of all three fluids. An increase in heat in leak parameter (Ht = Hb) value from 0 to 0.1 reduces hot fluid effectiveness by 32 per cent for an NTU value of 10.Originality ValueThe effect of heat-in-leak on a three-fluid cross-flow cryogenic heat exchanger is significant, but so far, no investigations are carried out. The results establish the efficacy of the method and throw light on important considerations involved in the design of such heat exchangers.