Appropriations shall not be required for refunds, as provided in RCW 43.88.170, nor in the case of payments other than for administrative expenses or capital improvements to be made from trust funds specifically created by law to discharge awards, claims, annuities and other liabilities of the state. Said trust funds shall include, but shall not be limited to, the accident fund, medical aid fund, retirement system fund, Washington state patrol retirement fund and unemployment trust fund. Appropriations may be required in the case of public service enterprises defined for the purposes of this section as proprietary functions conducted by an agency of the state. An appropriation may be required to permit payment of obligations by revolving funds, as provided in RCW 43.88.190.