Çalışma Akışkanlarındaki Gelişmeler

Rifrost
Yağ ve emülsiyon için tekrar Soğutma sistemlerin dışında, bütün diğer tekrar Soğutma sistemleri, su veya bir su glycol karışımının Soğutulması Kullanılır.Soğutma sisteminizini ilk kullanmaya başladığınızdan itibaren bulunması gereken sıvı kadar orantılı yada tamamen rifrost kullanılmalıdır.Su kalitesi ve başarılı sonuçların alınması için karışımın çok iyi yapılması lazım gelmektedir.Yada doğrudan rifrost kullanılmalıdır.Donmaya karşı korur,hem de bakterilerle ilgili büyümesini yok eder ve optimum korozyon korumasını sağlar.

Çalışma Akışkanlarındaki Gelişmeler

Güneş enerjili sıcak su hazırlama sistemlerinde toplayıcılarda absorplanan enerjinin hava
veya sıvı akışkanlar yardımıyla istenen depolama ortamına veya kullanıma aktarılması gerekir.
Donma tehlikesinin olmaması, korozif olmaması nedeniyle ideal bir ısı taşıma akışkanı olan hava,
ısı transfer özelliklerinin yetersizliği nedeniyle kullanım olumsuzluklarına sahiptir.
Çalışma akışkanı olarak su ise ucuzluk ve özellikler olarak (yüksek yoğunluk, yüksek ısınma
ısısı, düşük viskozite, korozif olmama, tutuşmazlık, zehirli olmama, yüksek kaynama noktası, ısı
transfer özellikleri gibi) uygun bir çalışma akışkanı olmasına karşın tek sorun donma noktasında
olan düşüklüktür. Bu sorunun çözümüne yönelik sistem tasarımları veya antifriz çözeltilerinin kullanımı
yoluna gidilmektedir. Ülkemizde uygulamalarda ve standartlarda önerilen diğer çalışma
akışkanları etil alkol ve su, etilen glikol ve su, propilen glikol ve su, mineral yağlan, silikon yağlan
farklı olarak önerilen çalışma akışkanlarıdır. Bu çalışma akışkanları ve kullanımları hakkında bilgiler ilgili kaynaklardan bulunabilir.
Endüstrinin birçok alanında gereksinim duyulan ısı veya soğu taşımada kullanılan çalışma kışkanları konusunda araştırmalar sürdürülmektedir. Bu amaçla da değişik kimyasallar üreten firmaların geliştirdiği özel çalışma akışkanları da bulunmaktadır. Özellikle güneş enerjisi uygulamaları için geliştirilen bazı çalışma akışkanlarının önemli özellikleri aşağıda verilmiştir.
Aynı firmanın ürettiği çalışma akışkanlarından, antifrogen N 52%, antifrogen L 52% çalışma
akışkanları da özellikleri bakımından güneş enerjisi ile düşük sıcaklık uygulamaları (T<100 color="red">Isıtma,Soğutma ve fire extingushing sistemlerinde kullanılan çok yönlü sistemleri

Antifreeze (Antifriz,Antifrogen)ürünleri merkezi ısıtma,yerden ısıtma,ısı pompası(heatpumps) ve ısı sistemlerinde iyileştirme için kullanılır.
Onlar, sızıntı bulma akışkan maddeleriyle beraber malzemeleri söndürüyor olan sistemler, güneşle ilgili ısıtma sistemleri ve ateşi serinletmek için hem de etkili akışkanlardır.
Onlar, glycol temel alınan çok yönlü sıcaklık transfer akışkan maddeleridir, glycol ve potasyum, formüllüdürler.

Rifrost, Antifrogen N

Bizim ürünlerimiz, uzun süreli donma korumasını taahüt eder, ve korozyona güvenilir şekilde karşı ısıtma ve soğutma sistemlerinizi korur.

Antifrogen N

Endüstriyel soğutma ekipmanları ve ürünleri için yüksek kaliteli bir ısı transfer sıvısı. Aynı zamnda normal soğutma ve salamura ısı transfer sıvısıdır.Etile glycolü temel alan üründür.
Başarılı bir şekilde kanıtlanmış ürün, Antifrogen N ®'in, açık bir sıvı olduğudur, soluk sarı renktedir.Güneşle ilgili ısıtmada,Isı pompası ve sıcak su ısıtma sistemleri, ve ssoğutma salamura olarak (Tuzlu çözüm) endüstriyel soğutma ürünlerinde,yüksek kaliteli bir ısı transfer sıvısıdır.

Antifrogen L

Gıda sanayisi için salamurayı, soğutma sistemlerini temel almıştır;
Korozyon korumasıyla güneşle ilgili ısıtma ısı pompası sistemleri için ısı transfer sıvısı olarak kullanılır.Antifrogen L ®, açık bir sıvıdır, soluk mavi renktedir.
Gıda sanayisinde soğutmada,salamurada,güneşle ilgili ısıtma ve ısı pompası sistemlerinde,orta sıcaklık ısı transferinde(Bira fabrikaları, süthaneler, dondurma fabrikaları ve balık işleme tabii tutma fabrikaları v.s.)kullanılabilir.Antifriz hareketi, toksikolojik olarak zararsızlığı 1.2-propilen ile glycol sağlanır.Antifrogen L ®'in Donma direnci, musluk suyuyla karışımındada( 100 mg/ kg klorüründen daha fazla içermemelidir.)değişir.Antifrogen L ®'in su ile karışımı enaz %25 olmalı dır.Bu oranda Donma noktası -10° C dir.

Antifrogen KF (VP 1974)

Gıda Sanayinde düşük sıcaklıktaki dolaylı soğutma sistemlerinde orozyon önleme ve düşük yoğunluklu salamuralaşmayı önleme sıvısı

Antifrogen SOL (VP 1981)

Güneş enerjisi uygulama sistemlerinde korozyondan, donmadan koruma ve yüksek sıcaklıklara dayanıklı hazır kullanımlı propilen glycol esas alınmış ısı transfer sıvısı

Protectogen

Kapalı çevrim ısıtma ve soğutma sistemlerinde korozyon önleyici konsantresi

Soğutma Grubları(Chiller) İçin En İyi Isı Transfer Akışkanları

The Best Heat Transfer Fluids for Liquid Cooling

Now that you’ve determined liquid cooling is the solution, do you know what heat transfer fluid to use? One of the most important factors when choosing a liquid cooling technology for your application is the compatibility of the heat transfer fluid with the wetted surfaces of the cooling components or system and your application. Heat transfer fluid compatibility is critical in ensuring long-term system reliability. Some other requirements for a heat transfer fluid may include high thermal conductivity and specific heat, low viscosity, low freezing point, high flash point, low corrosivity, low toxicity, and thermal stability¹. Based on these criteria, the most commonly used coolants for liquid cooling applications today are:

• Water
• Deionized Water
• Inhibited Glycol and Water Solutions
• Dielectric Fluids

By selecting a compatible pairing of heat transfer fluid and wetted materials, you’ll minimize the risk of corrosion as well as optimize your thermal performance. Copper is compatible with water and glycol/water solutions and aluminum is compatible with glycol/water solutions, dielectric fluids, and oils. When using deionized water or other corrosive fluids, however, stainless steel is generally recommended since it is more corrosion resistant than other metals. (See Table 1.) Most cooling systems are compatible with water or glycol/water solutions but require special plumbing for compatibility with deionized water or a dielectric fluid such as polyalphaolefin (PAO).

Table 1

MATERIALS & FLUID COMPATIBILITY
	Water	Glycols	Deionized Water	Dielectric Fluids (Fluorinert, PAO)
Copper	X	X		X
Aluminum		X		X
Stainless Steel	X	X	X	X

Water

Water is one of the best choices for liquid cooling applications due to its high heat capacity and thermal conductivity. It is also compatible with copper, which is one of the best heat transfer materials to use for your fluid path. Water used for cooling comes from different sources. Tap water, for example, comes from a publicly owned water treatment facility or a well. The benefit to using facility or tap water is that it is readily available and inexpensive. However, what is important to note about facility water or tap water is that it is likely untreated and is therefore likely to contain impurities. These impurities could cause corrosion in the liquid cooling loop and/or clog fluid channels. Therefore, using good quality water is recommended in order to minimize corrosion and optimize thermal performance.

Water’s ability to corrode metal can vary considerably depending on its chemical composition. Chloride, for example, is commonly found in tap water and can be corrosive. Facility or tap water should not be used in liquid cooling loops if it contains more than 25 PPM of chloride. The levels of calcium and magnesium in the water also need to be considered, since calcium and magnesium can form scale on metal surfaces and reduce the thermal performance of the components. (See Table 2.)

Table 2

MINIMUM REQUIREMENTS FOR GOOD QUALITY WATER2
Mineral	Recommended Limit
Calcium	<>
Magnesium	<>
Total Hardness	<>
Chloride	<>
Sulfate	<>

If you determine that your facility water or tap water contains a large percent of minerals, salts, or other impurities, you can either filter the water or can opt to purchase filtered or deionized water. If your facility or tap water is relatively pure and meets recommended limits, it is still generally recommended that you add a corrosion inhibitor for additional protection. Phosphate is an effective corrosion inhibitor for stainless steel and most aluminum components. It is also effective for pH control. One disadvantage of phosphate, however, is that it precipitates with calcium in hard water. For copper and brass, tolyltriazole is a common and highly effective corrosion inhibitor. For aluminum, organic acids such as 2-ethyl hexanoic or sebacic acid offer protection.

Deionized Water

Deionized water is water that has had its ions removed, including sodium, calcium, iron, copper, chloride, and bromide. The deionization process removes harmful minerals, salts, and other impurities that can cause corrosion or scale formation. Compared to tap water and most fluids, deionized water has a high resistivity. Deionized water is an excellent insulator, which is why it is used in the manufacturing of electrical components where parts must be electrically isolated. However, as water’s resistivity increases, its corrosivity increases as well. Deionized water will pH at approximately 7.0 but will quickly become acidic when exposed to air. The carbon dioxide in air will dissolve in the water, introducing ions and giving an acidic pH of around 5.0. Therefore, when using water that is virtually pure, it is necessary to use a corrosion inhibitor. When using deionized water in a recirculating chiller, special high purity plumbing is needed. The fittings should be nickel-plated and the evaporators should be nickel-brazed. When using deionized water in cold plates or heat exchangers, stainless steel tubing is recommended.

Inhibited Glycol and Water Solutions

The two types of glycol most commonly used for liquid cooling applications are ethylene glycol and water (EGW) and propylene glycol and water (PGW) solutions. Ethylene glycol has desirable thermal properties, including a high boiling point, low freezing point, stability over a wide range of temperatures, and high specific heat and thermal conductivity. It also has a low viscosity and, therefore, reduced pumping requirements. Although EGW has more desirable physical properties than PGW, PGW is used in applications where toxicity might be a concern. PGW is generally recognized as safe for use in food or food processing applications, and can also be used in enclosed spaces³.

Even though EGW’s thermal conductivity is not as high as water’s, EGW provides freeze protection that can be beneficial during use or during shipping. In fact, ethylene glycol is the chemical used in automotive antifreeze. However, automotive glycol should not be used in a cooling system or heat exchanger because it contains silicate-based rust inhibitors. These inhibitors can gel and foul, coating heat exchanger surfaces and reducing their efficiency. Silicates have also been shown to significantly reduce the lifespan of pump seals. While the wrong inhibitors can cause significant problems, the right inhibitors can prevent corrosion and significantly prolong the life of a liquid cooling loop. Inhibited glycols can be purchased from companies such as Dynalene, Houghton Chemical, or the Dow Chemical Company and are highly recommended over non-inhibited glycols.

As the concentration of glycol in the solution increases, the thermal performance of the heat transfer fluid decreases. Therefore, it is best to use the lowest possible concentration of inhibited glycol necessary to meet your corrosion and freeze protection needs. Dow Chemical recommends a minimum concentration of 25-30% EGW⁴. At this minimum concentration, the ethylene glycol also serves as a bacteriacide and fungicide. With recirculating chillers, a solution of 30% ethylene glycol will result in only about a 3% drop in thermal performance over using water alone but will provide corrosion protection as well as freeze protection down to -15°C (5°F).

The quality of the water used in the glycol solution is also important. The water should meet or exceed the limits specified in Table 2, even if you’re using an inhibited glycol. Ions in the water can cause the inhibitor to fall out of solution, resulting in fouling and corrosion.

Dielectric Fluid

While the food industry might be more likely to select PGW over EGW for heat transfer, the power electronics, laser, and semiconductor industries might be more likely to choose dielectric fluids over water. A dielectric fluid is non-conductive and therefore preferred over water when working with sensitive electronics. Perfluorinated carbons, such as 3M’s dielectric fluid Fluorinert™, are non-flammable, non-explosive, and thermally stable over a wide range of operating temperatures. Although deionized water is also non-conductive, Fluorinert™ is less corrosive than deionized water and therefore may be a better choice for some applications. However, water has a thermal conductivity of approximately 0.59 W/m°C (0.341 BTU/hr ft °F), while Fluorinert FC-77 has a thermal conductivity of only about 0.063 W/m°C (0.036 BTU/hr ft °F).⁵ Fluorinert is also much more expensive than deionized water.

PAO is a synthetic hydrocarbon used frequently in military and aerospace applications for its dielectric properties and wide range of operating temperatures. For example, the fire control radars on today’s jet fighters are liquid cooled using PAO. For testing cold plates and heat exchangers that will use PAO as the heat transfer fluid, PAO compatible recirculating chillers are also available. PAO has a thermal conductivity of 0.14 W/m°C (0.081 BTU/hr ft °F). So although dielectric fluids provide low risk liquid cooling for electronics, they generally have a much lower thermal conductivity than water and most water-based solutions.

Water, deionized water, glycol/water solutions, and dielectric fluids such as fluorocarbons and PAO are the heat transfer fluids most commonly used in high performance liquid cooling applications. It’s important to select a heat transfer fluid that is compatible with your fluid path, offers corrosion protection or minimal risk of corrosion, and meets your application’s specific requirements. With the right chemistry, your heat transfer fluid can provide very effective cooling for your liquid cooling loop. For more information on liquid cooling technologies, please contact Lytron. For more information on water chemistry or water purification, please consult with a chemical engineer or water quality specialist.

Written by Tracey Barber & Joao Castro, Lytron Inc

¹Mohapatra, Satish C., “An Overview of Liquid Coolants for Electronics Cooling,” ElectronicsCooling, May 2006, p. 22.

²The Dow Chemical Company, “The Importance of Using Good-Quality Water in Heat Transfer Fluid Solutions,” www.Dow.com , Form No.180-01396-1099QRP, October 1999.

³The Dow Chemical Company, “How to Choose the Right Heat Transfer Fluid”, Process Heating, January 2008, Troy, MI, p. 52.

⁴The Dow Chemical Company, “Engineering and Operating Guide for DOWTHERM SR-1 AND DOWTHERM 4000 Inhibited Ethylene Glycol-based Heat Transfer Fluids”, www.Dow.com , Form No. 180-1190-0901 AMS, September 2001, p. 6.

⁵3M, “3M Fluorinert™ Electronic Liquid FC-77”, www.3M.com , 98-0212-2309-8 (HB), May 2000, p. 1.