Session: 11-44-01: Heat and Mass Transfer for Renewable Energy Conversion Processes

Paper Number: 95703

95703 - Latent Heat Thermal Energy Storage in Shell and Tube With PCM and Metal Foam in LTNE With External Heat Losses 

Energy storage systems have become increasingly important in order to reduce environmental impact and to solve the problem of temporal and methodical mismatch between the energy demanded and the energy produced. There are two types of Thermal Energy storage (TES): Sensible and Latent. Latent TES systems have got high TES capacities per unit mass compared to the sensible ones; additionally, they operate with a small temperature range as the heat interaction occurs at quasi-constant temperature. Among these systems one of the most promising is based on PCMs. Although the performances of PCMs in LHTESS are seriously limited by their low thermal conductivities and poor heat transfer capability, the use of composite PCMs in LHTESS, in combination with metal foams, allows us to improve their low thermal conductivity and fully exploit their high energy density. In fact, using metal foams as matrices for thermal conductivity enhancement of thermal energy storage systems and adding PCMs inside it, the thermal conductivity of the latter is significantly improved. In that way, a thermal storage, with a fast-absorbing energy zone characterized by low thermal resistance, can be realized, even though the heat storage capacity of the composite MF-PCMs is slightly reduced.

In the present work, a numerical investigation on Latent Heat Thermal Energy Storage System (LHTESS) is performed on a vertical shell and tube geometry, made of a metal foam totally filled with a phase change material (PCM). In our simulation the PCM used is a pure paraffin wax and the metal foam is an aluminum one. The inner surface of the hollow cylinder is assumed to be at a constant temperature above the PCM melting temperature, the external surface to lose heat toward the outside external ambient, the top and bottom surfaces are considered adiabatic. The phase change process in the paraffin wax is modelled with the enthalpy-porosity theory, while the Local Thermal Non-Equilibrium (LTNE) and the Darcy-Forchheimer models are adopted to analyze the aluminum foam saturated by the paraffin. The numerical solutions of the governing equations are computed by means of Ansys-Fluent commercial code. For the simulations different foam structures such as porosity and pore density are analyzed together with different conditions for the heat transfer toward the external ambient. The results of numerical simulations, concerning LHTESS charging phase, are reported as a function of time and are compared in terms of melting time, average temperature, and energy storage rate. After all, they show that the presence of metal foam significantly improves the heat transfer in the LHTES system, giving a very faster phase change process with respect to pure PCM, reducing the melting time more than one order of magnitude. In addition, this numerical model can be further enlarged to simulate different types of metal foam and PCM.

Presenting Author: Renato Elpidio Plomitallo Università degli studi della Campania "Luigi Vanvitelli"

Presenting Author Biography: I am a Ph.D. student in Industrial Engineering at Università degli studi della Campania "Luigi Vanvitelli". In particular my course is related to Energy Conversion. One of mine research goals is to study the Thermal Energy Storage systems with PCM and metal foams during my Ph.D. course .

Authors:

Bernardo Buonomo Università degli studi della Campania "Luigi Vanvitelli"
Maria Rita Golia Università degli studi della Campania "Luigi Vanvitelli"
Oronzio Manca Università degli studi della Campania "Luigi Vanvitelli"
Sergio Nardini Università degli studi della Campania "Luigi Vanvitelli"
Renato Elpidio Plomitallo Università degli studi della Campania "Luigi Vanvitelli"