Heat transfer to suspensions of different grades of wood pulp fibres at different concentrations were investigated over a range of flow rates. It was observed that a small amount of fibre in suspension causes drag reduction and reduces the heat transfer coefficient below that for water. Both effects are a function of concentration, flow rate and fibre type. The more flexible fibres produce a greater level of drag reduction and a greater lowering of heat transfer coefficient. The measurement of heat transfer coefficient provides a method of comparing fibres of different flexibility for papermaking.