An Experimental Investigation into Diesel Engine Exhaust Waste Heat Recovery for Water Purification

Abstract

About 30% of the total combustion heat of an IC engine is carried away by the outgoing exhaust flue gases. This exhaust waste heat can be used for the purification of water. In the present work, a waste heat recovery cum water purification unit consisting of horizontal tube submerged evaporator and water cooled condenser was designed, fabricated and integrated to a 3.5 kW variable compression ratio diesel engine to perform purification of ground water. For this analysis, four hand pump water samples were collected from different areas of the ‘Malwa’ region of Indian Punjab viz. Kotkapura, Faridkot, Sri Muktsar Sahib and Bathinda. The collected water samples were tested for physico-chemical parameters and presence of heavy metals before and after performing distillation. The TDS content and level of some of the heavy metals like Zn, Pb and Fe were found to be quite high in the collected water samples. The experiments for distilled water collection rate were performed at four different compression ratios viz. 12:1, 14:1, 16:1 and 18:1 and at five loading conditions i.e. 2 kg, 4 kg, 6 kg, 8 kg and 10 kg. The distilled water collection rate was found to be directly proportional to the amount of recoverable heat from the diesel engine. The maximum and minimum collection rate observed were 2.75 LPH and 0.22 LPH noted respectively at CR – 12:1 / 10 kg load and CR – 18:1 / 2 kg load. The level of physico-chemical parameters and heavy metals in the resulting distilled water was found to be well below the limits defined by WHO and BIS. In this work, a comparison between collected distilled and RO water with respect to purity level is also presented. At the end, a discussion into total cost and payback period of the proposed unit is made. The payback period for the normal working of 8 hours per day, at maximum collection rate was found to be 2 years. This proposed water purification unit can be integrated with stationary IC engines, ships etc. for water purification / desalination purpose, thus, can impact a large population of the world.