Compact plate-fin heat exchangers (PFHE) having very high effectiveness (>0.95) are key equipment of modern helium liquefaction / refrigeration systems. Effectiveness (ε) of these heat exchangers strongly influences the overall system performance. Apart from basic fluid film resistances, various secondary parameters such as axial heat conduction (AHC) through the heat exchanger metal matrix, parasitic heat in-leak from surroundings, variation in fluid/ metal properties and flow mal-distribution etc need to be considered while sizing/ rating such high effectiveness PFHE. Need of multiple streams in a single heat exchanger further complicates thermal designs. In-house codes are developed at BARC/IIT Bombay for rating of such high effectiveness PFHEs. For experimental performance evaluation of PFHEs, their characterization at various operating conditions and validation of in-house developed numerical codes, a dedicated closed loop experimental test facility is developed. Development of the dedicated closed loop experimental test facility is presented in this paper along with initial test results.