Single phase and boiling heat transfer under steady and pulsating confined jet impingement

Computational and experimental investigations are carried out on steady and pulsating jet impingement heat transfer. The studies focus on the fundamental investigation of heat transfer with and without boiling phenomena, applicable in the area of electronic cooling. The novelty of the research is the exploration of the relative significance of the contributing fluid and heat transport mechanisms under different parametric conditions

LIC-GAN: Language Information Conditioned Graph Generative GAN Model

Deep generative models for Natural Language data offer a new angle on the problem of graph synthesis: by optimizing differentiable models that directly generate graphs, it is possible to side-step expensive search procedures in the discrete and vast space of possible graphs. We introduce LIC-GAN, an implicit, likelihood-free generative model for small graphs that circumvents the need for expensive graph matching procedures. Our method takes as input a natural language query and using a combination of language modelling and Generative Adversarial Networks (GANs) and returns a graph that closely matches the description of the query. We combine our approach with a reward network to further enhance the graph generation with desired properties. Our experiments, show that LIC-GAN does well on metrics such as PropMatch and Closeness getting scores of 0.36 and 0.48. We also show that LIC-GAN performs as good as ChatGPT, with ChatGPT getting scores of 0.40 and 0.42. We also conduct a few experiments to demonstrate the robustness of our method, while also highlighting a few interesting caveats of the model.Comment: 15 pages, 8 figure

Hierarchical Prompting Assists Large Language Model on Web Navigation

Large language models (LLMs) struggle on processing complicated observations in interactive decision making tasks. To alleviate this issue, we propose a simple hierarchical prompting approach. Diverging from previous prompting approaches that always put the full observation (e.g. a web page) to the prompt, we propose to first construct an action-aware observation which is more condensed and relevant with a dedicated SUMMARIZER prompt. The ACTOR prompt then predicts the next action based on the summarized observation. While our method has broad applicability, we particularly demonstrate its efficacy in the complex domain of web navigation where a full observation often contains redundant and irrelevant information. Our approach outperforms the previous state-of-the-art prompting mechanics by 6.2% on task success rate, demonstrating its potential on interactive decision making tasks with long observation traces.Comment: EMNLP 2023 Findings; Natural Language Reasoning and Structured Explanations Workshop at ACL 202

WebArena: A Realistic Web Environment for Building Autonomous Agents

With advances in generative AI, there is now potential for autonomous agents to manage daily tasks via natural language commands. However, current agents are primarily created and tested in simplified synthetic environments, leading to a disconnect with real-world scenarios. In this paper, we build an environment for language-guided agents that is highly realistic and reproducible. Specifically, we focus on agents that perform tasks on the web, and create an environment with fully functional websites from four common domains: e-commerce, social forum discussions, collaborative software development, and content management. Our environment is enriched with tools (e.g., a map) and external knowledge bases (e.g., user manuals) to encourage human-like task-solving. Building upon our environment, we release a set of benchmark tasks focusing on evaluating the functional correctness of task completions. The tasks in our benchmark are diverse, long-horizon, and designed to emulate tasks that humans routinely perform on the internet. We experiment with several baseline agents, integrating recent techniques such as reasoning before acting. The results demonstrate that solving complex tasks is challenging: our best GPT-4-based agent only achieves an end-to-end task success rate of 14.41%, significantly lower than the human performance of 78.24%. These results highlight the need for further development of robust agents, that current state-of-the-art large language models are far from perfect performance in these real-life tasks, and that WebArena can be used to measure such progress.Comment: Our code, data, environment reproduction resources, and video demonstrations are publicly available at https://webarena.dev

Google Search Trends to Assess Public Interest in and Concern About Vuity for Treating Presbyopia

PURPOSE: To assess public awareness, interest, and concerns regarding Vuity (1.25% pilocarpine hydrochloride ophthalmic solution), an eye drop for the treatment of presbyopia, based on Google Trends. METHODS: We used Google Trends that provides a relative search volume for queried terms, to evaluate searches for Vuity from June 30, 2021, to June 30, 2022, in the United States. The data for this study were downloaded on June 30, 2022. Main outcome measures were changes in relative search volumes for the terms Vuity, Eye drops for reading, Eye drops for near vision, Presbyopia, Pilocarpine, and related popular search terms, such as Vuity side effects, and Vuity retinal detachment . RESULTS: Since the approval of Vuity on October 29, 2021, notable increases in the relative search volumes occurred for Vuity in October 2021, December 2021, and from March to April 2022, which coincided with its approval, availability, and subsequent direct-to-consumer advertising based on positive results of clinical trials. The direct-to-consumer advertising had the greatest impact on the search volume for Vuity. Specific interests included Vuity cost, where to buy it, and its side effects. Retinal detachment was the most highly searched Vuity side effect. Geographic variation was evident, with the relative search volumes highest for Vuity in Wyoming, followed by North Dakota. CONCLUSION: Google Trends is a useful tool for monitoring increases in public interest in Vuity for presbyopia. Public concerns regarding side effects warrant further real-world investigations of the causal relationship between Vuity and retinal detachment

Transient Characteristics of Confined Submerjed Laminar Jet Impingement Heat Transfer from a Vibrating Heater

This paper presents the results of an investigation on the effects of applied surface-vibrations on forced convective heat transfer due to a confined submerged impinging two-dimensional laminar air-jet, for different nozzle-to-heater distances. A new dimensionless parameter representing the frequency of applied vibration is introduced. A comprehensive understanding of the effect applied surface vibrations for non-dimensional nozzle-to-heater distances of H = 1 & 8 is delineated with a parametric study for non-dimensional amplitudes of A = 0.05 & 0.2 and non-dimensional frequency of vibrations in the range 0 ≤ F ≤ 12.8, for a fixed jet Reynolds number of 500. Both instantaneous and time-averaged characteristics of flow and heat transfer are discussed, along with graphical results. It was found that the effect of surface vibrations were larger for smaller values of H, for any given values of other controlling parameters

Effect of standoff distance on the partitioning of surface heat flux during subcooled jet impingement boiling

Heat transfer involving boiling of impinging jets are used for cooling components that dissipate very large heat fluxes, typically over 100 W/cm2 concentrated at discrete locations. Several industrial applications requiring cooling of discretely heated components such as in power electronics, synchrotron x-ray, fusion, and semiconductor laser systems have found beneficial use of boiling impinging jets, particularly due to the large heat transfer coefficients obtained in the stagnation region. The present paper aims to investigate the effect of standoff distance on the partitioning of the surface heat flux during subcooled and confined submerged jet impingement boiling, for different heater sizes. The RPI wall-boiling model is employed for the partitioning of surface heat flux into liquid phase convective, quenching and evaporative heat fluxes, and solved in conjunction with the governing equations for flow and heat transfer. It is found that the standoff distance influences the characteristics of boiling only in the partial nucleate boiling regime. Besides, the influence was only on the liquid phase convective component of the total heat flux, while the quenching and evaporative components remained unaffected. The total heat flux in the partial nucleate boiling regime was consistently larger for smaller standoff distances, irrespective of the heater size. The change in the surface averaged liquid phase convective heat flux with change in standoff distance was also found to be larger for relatively smaller heater sizes in the partial nucleate boiling regime

Effect of heater size and Reynolds number on the partitioning of surface heat flux in subcooled jet impingement boiling

The overall heat transfer rate due to boiling of an impinging subcooled liquid jet is attributed to several simultaneous mechanisms including liquid and vapor phase convection, quenching (transient convection) and evaporation. In the present research, the Rensselaer-Polytechnic Institute (RPI) wall-boiling model is employed to carry out computational simulations on subcooled turbulent jet impingement boiling of water in a confined and submerged configuration. The effects of the controlling parameters, viz. heater-nozzle size ratios (wH/wN), degree of surface superheats (ΔTsat), jet-Reynolds numbers (Re) are studied on the partitioning of the total heat flux into liquid phase convection, quenching (transient convection) and evaporation. The effects of these controlling parameters were studied in the ranges 1 ≤ wH/wN ≤ 11, −5 °C ≤ ΔTsat ≤ 25 °C (heat fluxes upto 200 W/cm2) and Re = 2500 and 3750, for isothermal and isoflux heaters. The present computational approach was validated by comparison of the local temperature distribution on the heater, and boiling curves against experimental data in literature for axisymmetric and slot jets. The liquid phase convective and quenching components of the total heat flux were found to be larger for relatively lower values of wH/wN, implying smaller heaters. On the contrary, the evaporative counterpart was found to be smaller for relatively smaller heaters upto about wH/wN = 3, beyond which the change was negligible with increase in wH/wN.Beyond a threshold surface superheat, the heat flux due to quenching was found to be the largest contributor to the total heat flux; and this threshold value of surface superheat decreased almost exponentially with increase in heater size. It was also observed that irrespective of the heater size, the liquid phase convective component of the total heat flux for Re = 3750 was consistently larger as compared to Re = 2500, while the quenching and evaporative components of the total heat flux were nearly equal for both Reynolds numbers. An artificial neural network (ANN) was trained and tested with data sets generated from the present research, and ready-to-use weights are presented

Experimental Study of Low Frequency Pulsating Liquid Jet Impingement in a confined planar geometry

The use of pulsating impinging jets has been found to have both enhancing as well as deteriorating heat transfer characteristics as compared to traditional steady state jets, depending on the operating conditions. Liquid jet impingement is preferred over air jets for several applications due to their substantially much larger heat transfer coefficients. While there is considerable literature on heat transfer characteristics associated with pulsating air jet impingement, that on the effect of jet pulsations for submerged liquid jet impingement cooling configurations is sparse. An experimental investigation is thus carried out to study the effect of pulsation frequency and amplitude for submerged slot jet impingement cooling of de-ionized water on a heated aluminium surface for Reynolds numbers in the range 500 - 3400, frequencies of 0.25 Hz and 0.5 Hz, and amplitudes of 50% and 100% of mean flow. In addition, steady state experiments were also carried out for 800 ≤ Re ≤ 7000 for three different jet inlet temperatures 34.83 °C, 39.68 °C and 44.54 °C. For the range of parameters studied, it was found that the effects of jet pulsations are only marginal on the time-averaged heat transfer characteristics. While the effect of jet pulsations was negligible for Reynolds numbers up to 1000, a slight decrease (up to 12%) was observed in the Nusselt number for larger Reynolds numbers with jet pulsations