Experimental Observations of the Effects of Intermolecular Van der Waals Forces on Entropy

TL;DR

This paper experimentally investigates how intermolecular Van der Waals forces affect the entropy of non-ideal carbon dioxide, leading to an empirical model that improves internal energy predictions and enables a theoretical Stirling engine surpassing Carnot efficiency.

Contribution

It introduces an empirical equation for internal energy change in non-ideal fluids, improving upon previous entropy-based estimates and demonstrating a theoretical super-efficient Stirling cycle.

Findings

Empirical equation outperforms previous models in accuracy.

Non-ideal CO2 can theoretically power a Stirling engine exceeding Carnot efficiency.

Experimental measurements validate the new internal energy model.

Abstract

An experimental effort was conducted to measure the change in internal energy of non-ideal carbon dioxide as its volume rapidly expanded with the sudden opening of a valve from one to two compressed gas cylinders. This was achieved by measuring the mass heat capacity of the gas cylinders and the manifold-valve, and measuring the change in temperature from the sudden doubling of volume of the non-ideal carbon dioxide. It was determined that an empirical equation for the change in internal energy of a non-ideal fluid was more accurate than previous methods used for estimating the change in internal energy by estimating the change in entropy. With this empirical equation, a theoretical ideal Stirling cycle heat engine that exceeds the Carnot efficiency was realized by utilizing non-ideal carbon dioxide as a working fluid.