The model describes mass and energy balance equations, as well as heat transfer rate equations, for all the components and results in steam economy, improving up to 2.46 at evaporator inlet temperatures of 90 and 76 \({}^{\circ}\)C for the first and second effect. [PERSON] et al. [14] have designed a multiple-effect evaporator desalination process with different configurations using a Matlab model. Their results verified the development of a very accurate model (maximum relative error \(\sim\)0.7%) for MEE processes, including a large matrix solved for temperatures and flow rates of brine and vapor for all the units in any given configuration, such as forward, backward, parallel and mixed plants. In MSF technology, several simulation models have been developed and applied for optimal operation in desalination systems [15; 16; 17], including daily operational cost optimization, design (number of stages) and operation (rejected seawater and brine recycle flowrate) optimization and daily productivity optimization. A spray flash evaporation system, combined with a hybrid latent heat storage technology in order to develop an energy-saving desalination system that stores intermittent thermal energy, such as waste heat, solar heat or heat from the surplus steam of a power station, at night and utilizes the stored energy not only for the generation of process steam from seawater for industries and domestic air conditioning but also for the production of freshwater from the generated steam for industrial and domestic uses on-demand, has also been developed and evaluated by [PERSON] et al. [18]. Their research resulted in more than 95% usage of the amount of stored energy for process steam and freshwater production, confirming a high efficiency system. [PERSON] et al. [19] have conducted an energy and exergy analysis and performance evaluation of a vacuum evaporator for solar thermal power plant MLD systems. In their research, the effect of the dimensional and operating parameters on the freshwater flow rate, exergy efficiency and power consumption were investigated, concluding that the amount of produced freshwater flow rate is independent of the recirculating flow rate and is a function of the evaporator's volume. Another result of their investigation was that, with the brine concentration increase, a decrease in the produced freshwater flow rate and in the total power consumption was noticed and that the increase in the volume of the vacuum evaporator led to a freshwater flow rate increase. Finally, [PERSON] [20] presented a techno-economic evaluation of a ZLD system, using multi-effect distillation with thermal vapor compression operating at 120 \({}^{\circ}\)C, simulating the system and estimating a freshwater cost of about 4 US$/m\({}^{3}\). As noticed in the international literature, most of the research concentrates on the VMD and vacuum distillation systems coupled with solar or geothermal heat sources, while the use of the heat pump as a heat source remains relatively unexplored. The current research attempts to combine high-efficiency and eco-friendly technologies for brine treatment in order to enhance the freshwater production and eliminate the environmental and cost impact because of the brine rejection, which could be applied in small islands with limited habitants and varying demand in winter and summer. The innovation of the proposed system consists of the heating of the brine before it enters the flash tank, taking advantage of the rejected heat for the condensation of the refrigerant on the HP side, and in parallel, the system makes use of the latent enthalpy of the vapor that flows out of the flash tank, evaporating the refrigerant of the heat pump. More specifically, the combination of a high-temperature heat pump (HTHP) with a brine treatment technology based on evaporation under a vacuum is investigated, focusing on the parameters affecting the freshwater production and the electrical energy consumption.