A sublimation heat engine

Abstract

Heat engines are based on the physical realization of a thermodynamic cycle, most famously the liquid–vapour Rankine cycle used for steam engines. Here we present a sublimation heat engine, which can convert temperature differences into mechanical work via the Leidenfrost effect. Through controlled experiments, quantified by a hydrodynamic model, we show that levitating dry-ice blocks rotate on hot turbine-like surfaces at a rate controlled by the turbine geometry, temperature difference and solid material properties. The rotational motion of the dry-ice loads is converted into electric power by coupling to a magnetic coil system. We extend our concept to liquid loads, generalizing the realization of the new engine to both sublimation and the instantaneous vapourization of liquids. Our results support the feasibility of low-friction in situ energy harvesting from both liquids and ices. Our concept is potentially relevant in challenging situations such as deep drilling, outer space exploration or micro-mechanical manipulation.

Toward Low‐Frequency Mechanical Energy Harvesting Using Energy‐Dense Piezoelectrochemical Materials

“…This piezoelectrochemical coupling has been studied in a few electrochemical systems, most notably in lithium-silicon alloying systems, [ 17 ] lithium-graphite systems, [ 18 ] sulfuric acid-graphite systems, [ 19 ] and lithium cobalt oxide-graphite battery pouch cells. [1][2][3][4][5] The best conventional mechanical energy harvesting methods typically rely on piezoelectric materials for the conversion of mechanical energy from ambient vibration sources to electrical energy. [21][22][23] We describe the coupling here in terms of a coupling factor k , which is defi ned as the change in equilibrium potential U 0 of an electrochemical reaction with respect to change in applied stress σ .…”

Vibrations and Spatial Patterns Change Effective Wetting Properties of Superhydrophobic and Regular Membranes

“…The resultant viscous forces entrain the droplet in the same direction (Figure 5b) [33][34][35]. The self-propulsion effect has potential application, such as in a sublimation heat engine [36].…”

“…π " c solute RT (36) where c solute is the molar concentration of the solute in the solution, R is the gas constant, and T is the absolute temperature. When an external pressure greater than the osmotic pressure π is applied to reverse the flux of solvent molecules then the process is called reverse osmosis (RO).…”

Leidenfrost transition temperature for stainless steel meshes

“…Recently, there has been a strong resurgence in interest in the topic, which can be viewed as an example of perfect superhydrophobicity since a levitating droplet can be viewed in some respects as a droplet on a surface with a contact angle of 180 o [5][6][7]. Examples of recent reports include Leidenfrostinduced drag reduction [8], ratcheted surfaces for droplet self-propulsion [9][10][11][12][13][14], stabilisation of Leidenfrost vapour layers by superhydrophobic surfaces [15] and a sublimation heat engine [16]. In the majority of these cases, a common aspect is the combination of some form of surface texture or roughness on a substrate, always rigid, with the Leidenfrost effect.…”