As of today, the Multi Stage Flash (MSF) evaporator capacity has reached to 20 MIGD of desalinated water using traditional brine recycle and cross tube bundle configuration. However, on the way of scaling-up evaporator unit production beyond 20 MIGD, there are some technical barriers and economical aspects that need to be considered. This work presents a techno-economic comparison between long tube (LT) and cross tube (CT) bundles of MSF evaporator for a unit production of equal and greater than 20 MIGD. Process calculations showed that the heat transfer surface area of MSF-LT is 25% lower than that of MSF-CT. This is mainly owing to an enhancement in heat transfer process. The pumping power in LT evaporator decreases by 8% due to the lower friction loss. For a large size project of 100 MIGD, the saving in the total capital investment of MSF-LT evaporator is 15% lower than that of MSF-CT. The operating cost is the same. A novel layout of MSF-LT configuration is proposed in which the stages are arranged in triple decks to reduce the footprint up to 51%. The novel configuration enables a significant reduction in the water box size and numbers. (C) 2013 Elsevier B.V. All rights reserved.