Measurement of thermal conductivity of fluid using single and dual wire transient techniques Siddharth Komini Babu 1 , K.S. Praveen 1 , B. Raja ⇑ , P. Damodharan 1 Indian Institute of Information Technology, Design and Manufacturing (IIITD&M) Kancheepuram, Chennai 600 127, India article info Article history: Received 20 August 2012 Received in revised form 7 February 2013 Accepted 13 May 2013 Available online 25 May 2013 Keywords: Transient hot wire Platinum Thermal conductivity Dual wire method abstract A modified measurement device to measure thermal conductivity of fluids using transient hot-wire technique has been designed, developed, tested and presented in this paper. The equipment is designed such that the thermal conductivity could be measured using both single wire sensor of different length and dual wire sensor. The sensor, which is also a hea- ter, is a platinum micro-wire of 50 lm diameter. The influence of wire length on the mea- surement of thermal conductivity of fluids is tested using two single wires of length 50 mm and 100 mm. The thermal conductivity is also measured using a dual hot wire arrange- ment; which is achieved by placing the 100 mm and 50 mm wires in a Wheatstone bridge with the 100 mm wire as the sensor and 50 mm wire as a compensation wire. The appara- tus requires a 100 ml of test fluid to perform the experiment. The testing temperature of the test fluid during the experimentation can be suitably varied by the choice of heat exchange fluid used in the apparatus. Water is chosen as testing fluids for primary stan- dards. When compared to single wires, the thermal conductivity of the fluids measured is consistent with dual-wire method with an uncertainty of ±0.25%. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The thermal conductivity of fluids is the most essential parameter required for thermal design and its consider- ation. Laser flash method [1], thermo reflectance tech- niques [2], 3-omega technique [3–5] etc. techniques are gaining importance since it measures properties based on either steady state or pseudo steady state solutions. Traditionally, transient hot wire techniques; which uses Fourier’s transient heat conduction model, is a well-estab- lished method for accurate measurement of thermal con- ductivity over a wide variety of substances such as solids [6], polymers [7,8], and molten substances [9]. Among these samples, determining the thermal conductivity of fluid and gas samples is very complicated and delicate. Even though fluids and gases can transfer through conduc- tion, tend to invoke natural convection current which eventually superimposes the desired thermal conductivity value achieved using Fourier heat conduction. A variety of instruments have been modified and improvised in the past for better accuracy of thermal conductivity of fluids using hot wire technique [10–16]. In principle the method can be used to obtain both the thermal conductivity and the thermal diffusivity using the same experiment. It is seen that the wire diameter, length and material, nature of the fluid, material of construction, modes of heat trans- fer, electrical conductivity of the fluid etc. plays a vital role in measuring the thermal conductivity of the fluid accu- rately. In this paper a redesign of the hot wire apparatus that could used to measure the thermal conductivity of liq- uids is presented. 0263-2241/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.measurement.2013.05.017 ⇑ Corresponding author. Tel.: +91 044 27476355; fax: +91 044 27476301. E-mail addresses: siddhukb@gmail.com (S. Komini Babu), nanopra- veeniiitdm@gmail.com (K.S. Praveen), rajab@iiitdm.ac.in (B. Raja), da- modharan@iiitdm.ac.in (P. Damodharan). 1 Tel.: +91 044 27476355; fax: +91 044 27476301. Measurement 46 (2013) 2746–2752 Contents lists available at SciVerse ScienceDirect Measurement journal homepage: www.elsevier.com/locate/measurement