Histone deacetylase inhibitors valproate and trichostatin A are toxic to neuroblastoma cells and modulate cytochrome P450 1A1, 1B1 and 3A4 expression in these cells

Histone deacetylase inhibitors such as valproic acid (VPA) and trichostatin A (TSA) were shown to exert antitumor activity. Here, the toxicity of both drugs to human neuroblastoma cell lines was investigated using MTT test, and IC50 values for both compounds were determined. Another target of this work was to evaluate the effects of both drugs on expression of cytochrome P450 (CYP) 1A1, 1B1 and 3A4 enzymes, which are known to be expressed in neuroblastoma cells. A malignant subset of neuroblastoma cells, so-called N-type cells (UKF-NB-3 cells) and the more benign S-type neuroblastoma cells (UKF-NB-4 and SK-N-AS cell lines) were studied from both two points of view. VPA and TSA inhibited the growth of neuroblastoma cells in a dose-dependent manner. The IC50 values ranging from 1.0 to 2.8 mM and from 69.8 to 129.4 nM were found for VPA and TSA, respectively. Of the neuroblastoma tested here, the N-type UKF-NB-3 cell line was the most sensitive to both drugs. The different effects of VPA and TSA were found on expression of CYP1A1, 1B1 and 3A4 enzymes in individual neuroblastoma cells tested in the study. Protein expression of all these CYP enzymes in the S-type SK-N-AS cell line was not influenced by either of studied drugs. On the contrary, in another S-type cell line, UKF-NB-4, VPA and TSA induced expression of CYP1A1, depressed levels of CYP1B1 and had no effect on expression levels of CYP3A4 enzyme. In the N-type UKF-NB-3 cell line, the expression of CYP1A1 was strongly induced, while that of CYP1B1 depressed by VPA and TSA. VPA also induced the expression of CYP3A4 in this neuroblastoma cell line

Heat transfer and pressure drop measurements of a novel baffle heat sink for power electronics cooling

Abstract: Electric vehicle drivetrains are becoming increasingly more compact. One of the strategies to reduce weight and volume is to combine the lubrication and cooling circuit. This however has the drawback that cooling needs to be done with the lubrication oil circuit, which poses a challenge for the power electronics. In this work, a novel baffle heat sink for power electronics cooling using laminar oil flows is proposed and experimentally tested. The baffles in four directions produce a swirling motion to break up thermal boundary layers and enhance heat transfer. Two baffle heat sink geometries and one optimized pin fin heat sink were tested experimentally. The baffle heat sinks both had higher pressure drops and lower thermal resistances than the pin fin heat sink at equal coolant flow rate. When looking at the thermal resistance at equal pumping power, one baffle heat sink had a 7% higher thermal resistance, while the other baffle heat sink showed a 17% lower thermal resistance. The baffle heat sink design thus can outperform an optimized pin fin heat sink, but a proper design of the baffle geometric parameters is required

CFD simulation and geometric optimization of a novel baffle heat sink for power electronics cooling

The electric drivetrain of an electric vehicle typically has two fluid circuits: an oil circuit for lubrication and a water-glycol circuit for cooling. Eliminating the water-glycol circuit can result in a more compact and lighter drivetrain. However, this requires the drivetrain components to be cooled with oil as coolant, which has inferior heat transfer properties compared to water-glycol mixtures. This is particularly challenging for the power modules in the power electronics unit, which exhibit some of the highest heat fluxes in the drivetrain. This study focusses on the design and optimization of a novel type of heat sink for laminar flows with baffles to guide the flow in four different directions. This has two main advantages: the baffles act as fins and increase the heat transfer area and they introduce a swirling motion in the oil thereby disturbing the boundary layers continuously. Computational fluid dynamics simulations using Ansys Fluent are performed to evaluate the thermohydraulic performance of the heat sink. The influence of design parameters such as the height and thickness of both fins and baffles and the baffle spacing in horizontal, upward and downward direction was evaluated by simulations with several combinations of the design space, considering manufacturing constraints. The optimization of the design showed that the fin thickness, horizontal baffle spacing and baffle length should be as small as possible, while there were optimal values for fin height, upward and downward baffle spacing, streamwise baffle spacing and baffle thickness. The simulations show that the thermal resistance of the baffle heat sink can be 19% lower than that of a benchmark pin fin heat sink at equal pumping power

Flow boiling in different flow regimes under transient heat flux

Flow boiling has great potential of becoming the prevalent method in various heat transfer applications, because it combines a high heat transfer rate with a relatively uniform surface temperature. The majority of the previous studies on flow boiling heat transfer applied a constant heat flux as boundary condition. However, many of the possible applications are subject to heat fluxes that vary with time, for example the cooling of electronics dissipating a non-constant heat flux or the heating of the working fluid in a concentrated solar power system which is dependent on the irradiation of the sun. Therefore, this study focusses on the effect of transient heat fluxes, more specifically a square waveform profile transient heat flux, on flow boiling of R245fa in a horizontal tube with an inner diameter of 17.12mm. The heat flux was applied by a constantan resistance wire wrapped evenly around the outside of the test tube. During each test, the average dissipated power was 650W, corresponding to an inner wall heat flux of 12.09kW/m². The oscillation amplitude tested was 30% of this 650W average heat dissipation and the oscillation periods considered were 10s, 20s and 30s. Three different combinations of mass flux and vapor quality led to three different flow regimes that were tested: annular, slug and intermittent flow. It could be concluded from the data that the annular flow regime exhibited the highest heat transfer coefficients. Furthermore, it seemed to depend on the flow regime whether the transient heating case resulted in an improved or declined heat transfer compared with constant heating

Experimental study on the thermohydraulic performance of oil-cooled heat sinks for power electronics

Using the lubrication oil in (hybrid) electric vehicles as both coolant and lubricant, thereby eliminating the need of a separate coolant circuit, can improve the overall efficiency of the cars. However, oil exhibits inferior heat transfer properties compared to conventional coolants (mainly higher viscosity, lower thermal conductivity and lower specific heat capacity). Therefore, it should be investigated whether the cooling of the drivetrain using oil is sufficiently performant. In this paper, the thermal and hydraulic performance of three oil-cooled heat sink designs (pin fin, straight fin and jet impingement) for power electronics are experimentally evaluated. It can be concluded that the straight fin heat sink exhibits the best hydraulic performance, but the pin fin heat sink has the best thermal and overall performance

Modelling of the refrigerant distribution in a critically charged propane heat pump cycle for performance evaluation

The investigation of heat pumps employing natural refrigerants as working fluids has gained substantial momentum, driven by increasingly stringent regulations addressing the global warming potential (GWP) and ozone depletion potential (ODP) of refrigerants. Propane (R290) stands out as an attractive option due to its low GWP and zero ODP. However, a major drawback of propane lies in its flammability. When using propane as working fluid, it will therefore be necessary to limit the total refrigerant charge within the system, without compromising on the heat pump performance. This study endeavors to address this challenge by developing a model of the refrigerant charge distribution in a critically charged heat pump system consisting of an evaporator, a compressor, a condenser, and an expansion valve. In the model, the charge distribution in the two heat exchangers is modelled in detail using a suitable void fraction correlation. For the compressor and expansion valve, a simplified model is employed, in which no refrigerant charge is calculated. Using an iterative procedure, the model can then be used to determine the coefficient of performance (COP), evaporator- and condenser pressure for a heat pump with an established total charge and heat capacity. The influence of different design and operation parameters, such as the degrees of subcooling and superheat, the volume ratio of the evaporator and the condenser, etc., can be assessed