Nem alma prosesinde buharlaştırıcı yapısının yoğuşma verimine etkisi
Effect of fin structure and surface type of the evaporator efficiency on dehumidification process
Yazar: GÖKHAN SIR
Danışman: PROF. DR. SEYHAN UYGUR ONBAŞIOĞLU
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Makine Mühendisliği Ana Bilim Dalı / Isı-Akışkan Bilim Dalı
Derece: Yüksek Lisans, 2012
Konu: Makine Mühendisliği = Mechanical Engineering
Dizin: Buharlaştırıcılar = Evaporators ; Isı pompası = Heat pump ; Yoğuşma = Condensation

Özet:
Günümüzde enerjide verimliliğin arttırılması, enerji kaynaklarının hızla azalması göz önünde bulundurulduğunda zorunluluk noktasına gelmiştir. Bu konuda önemi vurgulamak amacıyla Avrupa Birliği çerçevesinde enerji verimliliğinin arttırılması başlığı altında gerek hükümetler gerekse sivil toplum kuruluşlarının katılımıyla birçok yeni düzenleme ve yönergeler yayınlanmaktadır. Bu durum ise enerji verimliliğinin etkili olduğu sistemlerde yenilikçi fikirlerin, uygulamaların ve optimizasyonların geliştirilmesi zorunluluğunu doğurmaktadır.Bu yüksek lisans tez çalışmasında ısı pompalı kurutucu sistemlerinde enerji verimliliğini arttırmak için, nem alma prosesinde buharlaştırıcı yapısının yoğuşma verimine ve yoğuşma hızına etkisi incelenmiştir.Tez çalışması altı ana bölümden oluşmaktadır. Birinci bölümde çalışmaya başlama nedenleri ve çalışmaların bitiminde hedeflenen sonuçlar genel hatlarıyla açıklanmıştır.İkinci bölümde, söz konusu konu ile ilgili olarak gerçekleştirilen literatür araştırmaları gösterilmektedir. Yapılan literatür araştırması sonucunda daha önce yapılan çalışmaların çoğunlukla klima sektörüne yönelik çalışmalar olduğu görülmüştür. Söz konusu bu sebepten dolayı bu tez çalışmasında yer alan literatür çalışmalarında buharlaştırıcı üzerindeki kanat verimini ve yoğuşma verimini genel olarak ortaya çıkaran çalışmalar yer almaktadır.Üçüncü bölümde nem alma prosesinin genel hatlarıyla incelenmesi yer almaktadır. Bu durum kapsamında ısı pompalı sistemler, psikrometri, özgül nem ve bağıl nem kavramları, nemli havanın soğutulma işlemi, hidrofilik ve hidrofobik kaplamaların genel özellikleri bu bölümde yer almaktadır.Dördüncü bölümde, tez çalışmasında kullanılan deney tesisatı detaylı olarak açıklanmıştır. Ayrıca sistemin belirsizlik analizi, havanın giriş bağıl nemi değişiminin buharlaştırıcı üzerindeki yoğuşma verimi ve yoğuşma hızına etkisinin deneysel çalışmaları yer almaktadır.Beşinci bölümde sistem üzerinde yapılan analitik çalışmalar yer almaktadır.Altıncı ve son bölümde sonuçlar ve değerlendirmeler yer almaktadır.

Abstract:
Due to global warming and limitations in natural resources; efficient use of energy becomes the focus of both academic and industrial researches. Manufacturers of different areas reunited for the aim of producing less energy consuming products. In order to emphasize the importance of this issue, under the headline of energy efficiency increase many new regulations and directives with the participition of both goverments and non ? governmental organizations (civil society organization) within the framework of European Union has been published. This necessitates an enhancement in developing innotive ideas, applications and optimisations for the systems in which the energy efficiency is critical.Considering the daily energy consumption in domestic usage; household laundry tumble dryer is the most energy consuming appliance. Tumble driers are substantially operated according to an exhaust air principle or a condensation principle. In the case of an exhaust air use; an air flow is sucked in from the environment where dryer is placed and after being heated it is directed into the drum of the tumble drier containing laundry to be dried. Humidity is absorbed by the heated air flow and is subsequently returned to the enviroment.Recently; household tumble dryers may be classified into two types; air vented and condenser type tumble dryers. A conventional air vented dryer consists of a drum (where laundry is placed), a fan, a heater (using a resistive heating part or combusting some type of fuel such as natural gas), a motor to rotate the drum and a couple of ducts to exhaust the moist air to the outside. On the other hand; condenser tumble dryers use heat exchanger (namely, a condenser) where vapor in the humid air condenses into water that is collected either a drain pipe or a collection tank. This system is of a closed cycle does not require a venting duct to the exterior of the house. Today two types of condenser tumble dryers can be found on the market. This tumble dryers are air condenser dryers and heat pump dryers.In this thesis; energy efficiency of a new generation tumble dryer is studied which is called a heat pump dryers. In heat pump dryers, after passing through the tumble and the filter, humidified air is blown to the evaporator where its temperature is reduced below the dew point and condensation occurs. After the evaporator, the process air goes through the condenser where it is heated before being blown back to the tumble. In laundry dryer system, the main idea is condansate the water so the evaporator structure is the most effective for increasing the efficiency of a heat pump dryer system.In this study, for increasing the efficiency of a heat pump dryer system, the effects of the evaporator structure in condensation efficiency and condensation rate has been studied. Thesis study consists of six chapters.As described in the first chapter; in order to investigate the influence of evaporator structure on the condensation efficieny; temperature and air flow rate at the entrance of evaporator (respectively 38°C and 1,85 m/s) is kept constant while variable relative humidty of entering air, fin type (flat and wavy) and surface type (hydrophic and hydrophilic) of evaporator?s were investigated.Firstly, a literature search was performed and represented in the second chapter. As a result of this research it has been understood that most of the studies that had been completed are about air ? conditioning systems.Hence, the literature search includes the studies that put for the fin efficiency and condensation efficiency generally.In the third chapter, examination of dehumidification process is outlined. Heat pump system properties, psychrometric definitions such as specific humidity and relative humidity, cooling process of moist air and general properties of hydrophilic and hydrophobic coatings have been presented in this chapterIn the fourth chapter, the experimental system used in the study is described in detail. Furthermore, the uncertainty analysis of the system and the experiments that shows the effects of variation of the evaporator inlet relative humidity on the condensation efficiency and condensation rate take part in this chapter.Analytical studies about the system are shown in the fifth chapter.Finally in the sixth chapter; results are discussed in detail. As a summary of this thesis;Highest condensation efficiency was achieved with plain fin type evaporater for both in hydrophilic and hydrophobic surface coatings.Another important result was that; condensation rate is increased proportionally with the initial relative humidity.As a concluding remark; all experimental results showed in this thesis were obtained at constant air flow rate and temperature at the enterance of evaporator. As a result,?Air inlet relative humidity, condensation rate and condensation efficiency is an important factor values. As the value of the air inlet relative humidity, condensation, and condensation rate of efficiency increases.?The evaporators which fin form are plain and wavy, are coated with a hydrophobic types, condensation rate and condensation efficiency, changes in the air inlet relative humidity for all tests (65%, 70%, 80%), plain the fin type is more efficient than the wavy the fin type.?The evaporators which fin form are plain and wavy, are coated with a hydrophilic types, condensation rate and condensation efficiency, changes in the air inlet relative humidity for all tests (65%, 70%, 80%), plain the fin type is more efficient than the wavy the fin type.?The evaporators which fin type are wavy, coating type are hydrophobic and hydrophilic, condensation rate and condensation efficiency, changes in the air inlet relative humidity for all tests (65%, 70%, 80%), hydrophobic coated evaporators are more efficient than hydrophilic coated evaporators.?The evaporators which fin type are plain, coating type are hydrophobic and hydrophilic, condensation rate and condensation efficiency, changes in the air inlet relative humidity for 70%, 80% hydrophobic coated evaporators are more efficient than hydrophilic coated evaporators.?This analytic model results compared with experimental results, seen that the average accuracy of %96,75.For the future studies,?It is suggested to investigate the efficiency at variable flow rate and temperature (evaporator inlet).?Usage of different types of evaporators, different fin types ( slit, louver etc.) and coatings (gold epoxy etc.) will also improve the accuracy of the analytic model.