Şafak Melih Şenocak

Supercapacitor modules are limited not by thermal runaway but by cumulative self-heating, managed at module scale almost exclusively by active air cooling. This work reports passive thermal management of a four-cell series supercapacitor module, 10.8 V and 125 F, using undoped and vanadium nitride doped RT44HC and RT54HC paraffins. A 27-run campaign spanned PCM configuration, current at 15 and 25 A and ambient at 25 and 35 °C, with 25 thermocouples inside a chiller-regulated cabinet. A three-dimensional transient model reproduced all fifteen instrumented cases to a mean heating-phase root mean square error of 0.64 °C. At 25 A the module without PCM was stopped short of the 200-cycle duty at both ambient temperatures, whereas every PCM-filled configuration completed it without parasitic power, suppressing the peak by at least 9.4 to 14.4 °C for RT44HC and 4.5 to 4.9 °C for RT54HC. Even without melting the enclosure still cut the peak by 7.1 °C, through conduction and added mass alone. Vanadium nitride reached 2.9 °C at 2 wt% with melting fully engaged and stayed at or below 0.63 °C elsewhere, against a measured resolvable-difference threshold of 0.5 °C. Latent buffering carried a recovery penalty, extending the half-recovery time from 1671 to 6934 s, which nano-enhancement shortened to 5332 s. The validated model shows that surface sensors underestimate the interior most where cooling works best: the computed core exceeded the surface average by 5.85 °C with PCM against 0.28 °C without, and reached 66.7 to 67.4 °C for RT54HC while the surface read 58.8 to 59.5 °C. Melting-point matching dominated intrinsic property improvement, a 59 % conductivity gain producing no resolvable benefit because the melting window lay above the duty.

Paraffin phase change materials (PCMs) are limited by low thermal conductivity, commonly raised with nanofillers that often erode the specific heat. Here, vanadium nitride (VN), a metallic nitride best known as a supercapacitor electrode, was introduced as a conductivity filler and dispersed at 0.5-2.0 wt% in paraffin RT44HC by a surfactant-assisted two-stage melt-dispersion method, and the composites were characterised by XRD, FT-IR, FE-SEM/EDX, DSC, TGA and transient hot-wire thermal-conductivity analysis. DSC phase-change parameters are given as mean ±SD (n=3). The same dose was tested in a second, higher-melting matrix (RT54HC-2VN). XRD and FT-IR confirmed that VN retains its rock-salt structure and is physically dispersed, without new phases or chemical bonds. At 2 wt% VN, solid-phase thermal conductivity increased from 0.207 to 0.295 W/(m·K) (+42.5 %) and liquid-phase from 0.190 to 0.217 W/(m·K) (+14.2 %), while solid specific heat decreased only from 2.02 to 1.95 J/(g·K) (-3.5 %). The melting enthalpy was 246.9 J/g for pure RT44HC and 238.9 J/g at 2 wt% VN, with the melting onset unchanged (38.9 °C). The maximum decomposition temperature rose from 222 to 263 °C, and the melting enthalpy was unchanged after 1000 melt-freeze cycles (239 to 240 J/g). In RT54HC, 2 wt% VN raised solid conductivity by 41.3 % and preserved the specific heat (+2.9 %) where cubic boron nitride had lowered it by 19.4 %. This VN gain came at the cost of a 16 % latent-heat reduction. VN thus enhances paraffin-PCM thermal conductivity with a near-neutral specific heat, a balance well suited to passive thermal management of self-heating devices such as supercapacitors and power electronics.

This study tailors titanium nitride (TiN)-reinforced RT70 HC nanocomposite phase change materials (PCMs) for medium-temperature thermal energy storage. TiN nanoparticles were incorporated into commercial RT70 HC at 0.1–2.0 wt.% by a two-stage method combining sodium dodecyl sulfate, magnetic stirring, and ultrasonication, and characterized by FT-IR, XRD, SEM-EDX, elemental mapping, DSC, thermal conductivity, Cp, TGA, and 1000-cycle tests. FT-IR and XRD confirmed the physical integration of TiN into RT70 HC without new chemical bonds or secondary phases, and SEM-EDX showed a concentration-dependent dispersion. The phase change temperatures were largely preserved. The latent heat varied non-monotonically with TiN content, increasing at low loadings (0.1–0.5 wt.%) and decreasing at higher loadings. Because each composition was prepared as a single batch and measured on small specimens, the low-loading latent-heat increase (up to about 9%) is indicative rather than statistically proven and may fall within the subsampling variance. The 0.5 wt.% sample reached the highest values of 306/296 J/g in the first cycle and 286/268 J/g after 1000 cycles. The thermal conductivity increased with TiN content, reaching a maximum enhancement of about 24.09% in the liquid phase (0.1785 to 0.2215 W/(m·K) at 80 °C) and 35.7% in the solid phase at 2.0 wt.%, whereas the specific heat capacity was lower at higher loadings, an indicative trade-off given the single-run measurement uncertainty. TGA showed degradation onset temperatures above 240 °C, a wide safety margin relative to the ~72 °C working range. Overall, the 0.1–0.5 wt.% formulations offered the most balanced thermal performance for medium-temperature applications.

The need for cooling technologies increases tremendously with raising demand on the powerful and compact electronics. There, it pushes the research and technology to the new investigations on varying heat transfer mechanisms and devices. While one of these devices is vapor chamber (VC), an experimental study has been carried out to investigate the heat transfer performance of a VC under partial heating, varying heat fluxes, and different inclination angles for different temperatures, in the current study. For this purpose, a VC with a dimension of 90 mm × 90 mm × 3 mm is evaluated via its resulting thermal resistance, performance, and the temperature distribution over the VC surface. There, the limited effect of inclination angle is observed on the performance, while the highest change is obtained with decreasing local heating surface area, thus increasing heat fluxes. Moreover, this trend is seen almost similar with a reasonable shift up or down according to the different temperature differences.