Abstract

The washing machine has become an integral part of our urban daily life. Usually in western countries there is a separate washer and a dryer in the house. Nowadays customers prefer to have a combined product called as Combo which comprises washer and dryer. This leads to the challenge of managing the drying system in compact space. Year on year the expectation of the customers are raising in terms of the drying time and energy rating for running these machines. So it becomes of utmost importance to have a very efficient machine to dry the clothes with less time as well energy consumption should be low. In that regard, condenser play an important role in combo machines. The main function of condenser is to remove water from the humid air which comes from the clothing drum. So to improve the drying rate without affecting the energy consumption, it is always necessary to have maximum condenser efficiency. In combo washers and dryers generally water cooled condensers are used and since it is a combined unit, there is space constraint for placing the condenser. This project aims to predict early in the design cycle the performance of the water cooled condenser using Computational Fluid Dynamics (CFD) methodology. In this paper, heat transfer analysis is performed using a commercial CFD tool fluent in early stage. Trade off analysis done for different design parameters which can affect the performance of condenser like water flow rate, length, diameter, material of condenser tube, air flow rate and temperature. Critical thinking used through thought map and product map used to identify critical parameters. Virtual DOE used to analyze significant parameters and interaction of those parameters for maximizing the heat transfer rate across the air and condenser tube. Effect of these parameters over the pressure drop in the system is also analyzed to get the trade off between heat transfer and water side/air side pressure drop. In the second step, two phase analysis performed to understand the actual condensation phenomenon using the Eulerian wall film model for the baseline model. The work includes the simulation methodology for predicting the condensate rate by studying the different parameters like turbulence model, mesh method, solver parameter etc. This assessment shows the simulation prediction has a good correlation with the physical test results. Similar study performed for the best design evolved in the first step to understand the improvement in the condenser efficiency. The study encompasses developing a guideline for the simulation by identifying the optimum shape/design of the condenser unit in combo washer and dryer to improve the drying time.