Abstract— Solar water heater plays a vital role in energy conservation. Because of its efficiency is more than the electric conversion. It has become the well proven and established appliance for providing hot water requirements in thousands of families in India. Solar water heating is a very simple and efficient way to grab energy from the sun and use it. In spite of its low efficiency it occupies a respectful place among the energy users. Therefore any improvement in the construction and operation of solar water heating system would definitely result in saving conventional fuel and cost. The objective of this project is to create uniform velocity in solar water system by using variable header.The solar water heater is designed with a larger diameter of the header is 5.08 cm and smaller diameter of 2.54 cm with the length of 100 cm. The existing solar water heating systems the overall thermal performance reduces due to non-uniform flow in riser tubes. The overall thermal performance and efficiency is higher in variable header system due to uniform velocity.The experimental results are analysed with CFD analysis software and the results are compared with the existing solar water heating system. Keywords— Variable header , Solar water heating, riser tubes, CFD. I. INTRODUCTION OLAR water heater is a devise which is used to heat the water. Solar water heater plays a role in energy conservation. Solar water heaters are characterized by its thermal performance that depends on the transmittance, absorption and conduction of solar energy and the conductivity of the working fluid. Because its efficiency is more than the electric conversion. In conventional solar water heating system, the water flows in laminar regime. a Solar radiation is the heat input to the collector; water is used as the working fluid. The overall thermal performance and efficiency is higher in variable header due to uniform velocity one of the biggest uses of electricity, gas and oil is the heating of water home, and in offices, schools and hospitals etc. Solar water heating is a very simple and efficient way to grab energy from Dr. Jaisankar Subramanian, Principal, Star Lion College of Engineering &Technology, Thanjavur, Tamilnadu, India. corresponding author phone: +91437424232423; fax: +914374244244;(e-mail: jaisankar1312@gmail.com). Dr.Senthilkumar Tamilkozhndu, Professor, Department of Mechanical Engineering, Anna University of Technology, Tiruchirappalli, Tamilnadu, India (e-mail: kmtsenthil@gmail.com). Thulasi Selvam, Assistant Professor, Department of Mechanical Engineering, Anna University of Technology-Thirukuvali campus, Thirukuvalai,Thiruvarur,Tamilnadu, India. (e-mail: thulasi_ oxford @yahoo. com ). the sun and use it. Solar water heaters concentrate diffused solar radiation into thermal energy [1] . Hot water plays a vital role in human society. It is used for various applications in the day-to-day human life. The utility of hot water in India covers various applications which can be categorized under three main sectors, viz., and domestic, commercial and industrial. It is used for many applications like bathing, washing and drinking in flats, bungalows and apartments under the domestic sector. Solar water heating system with capacity of 50 to 100 liters per day has been installed in more than 30,000 homes through out India[2].Larger solar water heating systems are used in restaurants, canteens, guest houses, hotels, hospitals, hotels and dormitories under commercial sector. Similarly, water heating systems are used in process, dyeing, food industries and in thermal power plants for pre-heating the boiler feed water. The requirement of hot water per day for industrial and commercial sector is around 2, 40,000 liters. The overall installed capacity of thermal collectors in India is capable of producing around 25 million liters of hot water per day at 60- 70 0 c [3]. Fig.1 Hot water demand and supply Fig.2 shows the installed capacity of solar collectors till 2007. This figure clearly shows the ever increasing demand for hot water in India. The installed area of solar collectors in India is around 2.15 million square meters as on December 2007. The Government of India promotes the commercialization of solar collectors every year and they have approved 47 manufactures to produce these collectors based on the norms of the Bureau of Indian Standards [4]. Experimental Studies on Variable Header Solar Water Heating System Jaisankar Subramanian, Senthilkumar Tamilkozhndu, and Thulasi Selvam S 2nd International Conference on Mechanical, Production and Automobile Engineering (ICMPAE'2012) Singapore April 28-29, 2012 258