b'Manufacturing | Engineer Innovationtype). This results in an increase in the water temperature, from 10C to approximately 65C, after which the hot water is then directed to the top of the tank, near the hot water outlet, allowing an almost immediate availability of water at 65C.As a relatively new technology, the cost of parts for these CO -based systems is 2high compared to those in traditional (hydrofluorocarbon) electric heat pumps. As such, the need to minimize the time and costs required to take the technology to market is particularlyFigure 2: Detail of ducting geometry surrounding the evaporator and the corresponding acute. One way to meet this challengecomputational mesh (evaporator is marked as component 4 in left image, and is highlighted in is minimizing the reliance on physicalpurple on right image).prototypes in the development process, as they are very expensive (in additionheat pumps, the thermal and advancedaffects the efficiency of the to being slow to build and test). Atdevelopment engineers at SANDENevaporator.SANDEN, this meant using Simcenterhad established three well-defined STAR-CCM+ to automate the search forcriteria that must be satisfied toThe geometry of the ducting the best design for a critical componentmaximize the heat transfer in thesurrounding the evaporator is illustrated of the systemthe evaporator. evaporator: in Figure 2, along with the computational mesh used in the As illustrated in Figure 1, the evaporator1. The air velocity on the evaporatorSimcenter STAR-CCM+ simulations. A is a heat exchanger in which exterior airinterface should be as uniform ascentrifugal fan (component 6 in Figure flows over refrigerant-filled passages,possible; specifically, the standard2) draws exterior air through the resulting in the refrigerant (CO )deviation of the velocity magnitudeupstream duct (1), past the top suction 2absorbing heat from the exterior air.should be less than 0.28 m/s, section (2), into the suction chamber Better heat transfer in the evaporator(3), and through the evaporator (4). The results in better performance of the2. The velocity of the air flowingair is then drawn into the shroud (5), entire system. As such, it is critical tothrough the evaporator should notthen into the fan casing (7) before shape the passageways that direct airexceed 1.8 m/s, and finally being sent out by the fan (6) to through the evaporator in such a way asthe downstream duct (8). The twisting to maximize the heat transfer that3. The air recirculation ratio should bepath the air takes attests to the occurs in the evaporator. less than 5%. The recirculation ratiomagnitude of the design challenge, is defined as the percentage of awhich is magnified by the fact that the Design exploration, not justcross-section through which the airevaporator around which the duct is assessment of individual designs flows in the opposite direction afterbeing designed is quite small.Based on their years of experience inpassing through the evaporator; this the design of evaporators used in theseis to be minimized as it negativelyThe SANDEN engineers were already aware of the value of virtual prototypes and simulationthey had been Define Simulate Evaluate running Simcenter STAR-CCM+ simulations of the flow through the TraditionalInput Output TargetsFinal design evaporator for validating design approach met?Performance of single designvariants that they had developed based Baseline design (homogeneity of flow velocity, recirculation ratio,DOE / RSMon their own expertize. These were CFD simulation model max velocity) optimization validation runs carried out to Iterate understand the effects of individual design parameters, not necessarily to DesignBetterdrive the identification of new exploration Input Output designs,candidate designs. Even so, these runs Desired performanceFaster!(homogeneity of flow velocity,had already resulted in the recirculation ratio, max velocity) CFD-based design exploration Improved designs with (size, shape, physicalidentification of a good baseline Variable parametersSimcenter STAR-CCM+parameters)(size, shape,Design Manager design that met the maximum velocity physical parameters) criteria listed above (but not the other Figure 3: Traditional design approach versus design exploration. two).41'