1. A design support method for a heat convection field or a mass diffusion field, comprising: a modeling support step of modeling a designing space upon receipt of a signal from an input device operated by a user while displaying a predetermined image on a display device arranged to display a graphic image; a mesh generation step of generating a mesh on the designing space model; a forward analysis step of analyzing either a heat convection field or a mass diffusion field of the designing space model by solving an equation of the heat convection field or the mass diffusion field based on an initially set value of a designing parameter input through the input device regarding the meshed designing space model; a purpose setting step of setting a design purpose upon receipt of a signal from the input device while displaying a predetermined image on the display device; an inverse analysis step of analyzing a sensitivity defined by a change ratio of the design purpose with respect to a change in the designing parameter by solving an adjoint equation in correspondence with the design purpose based on the set design purpose; and a sensitivity display step of displaying information on the sensitivity analyzed by the inverse analysis as a graphic image on the display device; wherein the inverse analysis step includes the steps of: setting an objective function J defined as the following equation (1) as the design purpose; solving a following adjoint equation (3) in correspondence with the design purpose under the following boundary condition (4) and constraints defined as a following equation (2); and using a sensitivity represented by a following equation (5) obtained by the adjoint equation (3) J = âˆ« Î© â¢ f T â¢ â¢ â…† Î© + âˆ« Î© â¢ f C â¢ â¢ â…† Î© + âˆ« Î© â¢ f u â¢ â¢ â…† Î© + âˆ« Î© â¢ f p â¢ â¢ â…† Î© + âˆ« Î“ T â¢ g T â¢ â¢ â…† Î“ + âˆ« Î“ q â¢ g q â¢ â¢ â…† Î“ + âˆ« Î“ C â¢ g C â¢ â¢ â…† Î“ + âˆ« Î“ m â¢ g m â¢ â¢ â…† Î“ + âˆ« Î“ m â¢ g u â¢ â¢ â…† Î“ ( 1 ) L = J + âˆ« Î© â¢ [ p * , u * , T â¢ * , C * ] â¢ A â¡ ( p , u , T , C ) â¢ â…† Î© ( 2 ) A * â¡ [ p * , u * â¢ T * , C * ] T = [ âˆ‚ f p âˆ‚ p , âˆ‚ f u âˆ‚ u , âˆ‚ f T âˆ‚ T , âˆ‚ f C âˆ‚ C ] T â¢ â¢ T * = - âˆ‚ g T âˆ‚ q â¢ â¢ on â¢ â¢ Î“ T , â¢ q * = - âˆ‚ g q âˆ‚ T â¢ â¢ on â¢ â¢ Î“ q , â¢ q * = KT * â¢ â¢ on â¢ â¢ Î“ K ( 3 ) C * = - âˆ‚ g C âˆ‚ m â¢ â¢ on â¢ â¢ Î“ C , â¢ m * = - âˆ‚ g m âˆ‚ C â¢ â¢ on â¢ â¢ Î“ m , â¢ u * = - âˆ‚ g u âˆ‚ Ïƒ â¢ â¢ on â¢ â¢ Î“ u ( 4 ) Î´ â¢ â¢ J = âˆ« Î“ q â¢ T * â¢ Î´ â¢ â¢ q â¢ â¢ â…† Î“ + âˆ« Î“ T â¢ q * â¢ Î´ â¢ â¢ T â¢ â¢ â…† Î“ + âˆ« Î“ K â¢ ( T outside - T ) â¢ T * â¢ Î´ â¢ â¢ â…† K â¢ â…† â¢ Î“ ( 5 ) where f T , f C , f u , and f p : Functions regarding temperature mass concentration, flow rate, and pressure defined in a space Q; Î“ T , Î“ q , Î“ C , Î“ m , and Î“ u : Boundaries of the space Q in which the temperature heat flux concentration, diffusion flux, and flow rate vector are controllable; g T , g q , g C , g m , and g u : Functions regarding temperature, heat flux, concentration, diffusion flux, and flow rate vector defined on the respective boundaries of the space Q; A: A vector formed of governing equations of the field having the pressure p, the flow rate vector u, the temperature T and the concentration C as the dependent variables; p*, u*, T*, and C*: Adjoint pressure, adjoint flow rate, adjoint temperature, and adjoint concentration; A*: An adjoint operator matrix to a linear perturbation equation system; and Î´q, Î´T, Î´K, Î´m, Î´C, and Î´u: Influences of a heat flux change, a temperature change, an overall heat transfer coefficient change, a diffusion flux change, a concentration change, and a flow rate vector change on the boundary.