Answer Hello Sharon. A filter-drier WPW10143759 in a refrigeration or air conditioning system has two essential functions: one, to adsorb system contaminants, such as water, which can create acids, and two, to provide physical filtration. Evaluation of each factor is necessary to ensure proper and economical drier design. Hope this helps. Read More... Answered by AppliancePartsPros.com | Monday, August 22, 2011