Higher depletion rate and increasing price of fossil fuels have motivated many researchers to harness energy from the waste heat from internal combustion engines, and thus improve the overall efficiency. Among the waste heat recovery methods, the bottoming Rankine cycle is the most promising. In this technique, the recovered heat is used to produce additional power using turbine. In order to maximise the additional power production, an effective heat exchanger design is necessary. The main focus of the current research was to design heat exchangers which needed to be pancake-shaped to be retrofitted into a vehicle. The heat exchanges chosen were shell and U-tube type. CFD simulations were carried out to optimize the design of the heat exchangers and calculate the additional power that could be achievable by using this optimized pancake-shaped heat exchangers.