Investigation of The Effect of Using Different Type of Fin on The Melting Time of PCM in A Latent Thermal Energy Storage Unit Using CaCl2 .6H2O and Na2SO4.10H2O Phase Change Materials by CFD Analysis

Year 2023, , 701 - 723, 15.06.2023

Fadime Şimşek , Sefa Organ

https://doi.org/10.31466/kfbd.1277463

Abstract

In this study, a double tube concentric heat exchanger was designed to store thermal energy by utilizing the latent heat storage properties of CaCl2.6H2O (calcium chloride hexahydrate) and Na2SO4.10H2O (sodium chloride decahydrate) inorganic phase change materials (PCM). Computational Fluid Dynamics (CFD) analyzes were performed with the help of ANSYS Fluent commercial program for 50 0C, 60 0C and 70 0C ITA (heat transfer fluid) water temperatures selected in accordance with the operational waste heat values. With the two-dimensional and time-dependent analyzes, the PCM melting time analyzes were completed first in the finless state and then in the case of placing a different type of fin in the PCM in order to increase the heat transfer. Different from the literature, the fin effectiveness of 6,9,12,15 finned models, which were determined by ANSYS analysis as 2.2, 3.3, 4.4, 5.5, respectively, were at 60 °C, which was determined as the optimum waste heat temperature compared to the finless model. It was observed that CaCl2.6H2O melted in 140 minutes and Na2SO4.10H2O in 180 minutes in the finless state. The reason for this situation is that the thermal conductivity coefficient of CaCl2.6H2O is higher. With the increase in the number of fins compared to the finless condition, the melting times decreased by 71.42%, 75.71%, 79.28% and 82.14% for CaCl2.6H2O phase change material, and 73.33%, 77.77%, 80% and 81.66% for Na2 SO4.10H2O. According to the results of the analysis, it was determined that the melting time of PCM decreased with the increase in ITA temperature and the number of fins, and heat energy was transferred from heat transfer fluid to phase change material more quickly.

Keywords

Thermal energy storage, PCM, fin, melting time

CaCl2.6H2O ve Na2SO4.10H2O Faz Değişim Malzemelerinin Kullanıldığı Gizli Termal Enerji Depolama Ünitesinde Farklı Tip Bir Kanat Kullanmanın FDM’nin Erime Süresine Etkisinin HAD Analiziyle Araştırılması

Abstract

Bu çalışmada, CaCl2.6H2O (Kalsiyum klorür hekzahidrat) ve Na2SO4.10H2O (Sodyum klorür dekahidrat) inorganik faz değişim malzemelerinin (FDM) gizli ısı depolama özelliklerinden faydalanılarak termal enerji depolamak için çift borulu eşmerkezli bir ısı değiştiricisi tasarlanmıştır. Hesaplamalı Akışkanlar Dinamiği (HAD) analizleri, işletme atık ısı değerlerine uygun olarak seçilen 50 0C, 60 0C ve 70 0C ITA (ısı transfer akışkanı) su sıcaklıkları için ANSYS Fluent ticari programı yardımıyla yapılmıştır. İki boyutlu ve zamana bağlı olarak gerçekleştirilen analizlerle öncelikle kanatçıksız durumdaki, daha sonra ısı transferini arttırmak amacıyla FDM içerisine literatürden farklı bir tip kanat yerleştirilmesi durumundaki FDM erime süresi analizleri tamamlanmıştır. Kanat etkenlikleri sırasıyla 2,2, 3,3, 4,4, 5,5 olarak literatürden farklı bir şekilde ANSYS analiziyle tespit edilen 6,9,12,15 kanatlı modellerin, kanatsız modele göre optimum atık ısı sıcaklığı olarak belirlenen 60 °C sıcaklıkta erime prosesleri incelenmiştir. Kanatçıksız durumda CaCl2.6H2O’ın 140 dakikada, Na2SO4.10H2O' ün ise 180 dakikada erime gösterdiği görülmüştür. Bu durumun nedeni CaCl2.6H2O’nin ısıl iletim katsayısının daha yüksek olmasıdır. Kanatsız duruma göre kanat sayısının artmasıyla erime sürelerinin, CaCl2.6H2O faz değişim malzemesi için %71,42, %75,71, %79,28 ve %82,14, Na2SO4.10H2 O için ise %73,33, %77,77, %80 ve %81,66 oranında azaldığı belirlenmiştir. Analiz sonuçlarına göre, ITA sıcaklığı ve kanat sayısındaki artışla FDM ’nin erime süresinin azaldığı ve ısı transfer akışkanından faz değişim malzemesine daha hızlı bir şekilde ısı enerjisi aktarıldığı tespit edilmiştir.

Keywords

Termal enerji depolama, FDM, kanat, erime süresi.

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