Cooling is critical to preserve the required effectiveness and reliability in a large range of products such as automobiles, high and medium cogeneration power plants, high power laser systems. Part of heat load magnification and the heat fluxes induce by more industrial products, cooling is one of the industry's main technical troubles such as manufacturing, transport and in microelectronics. The main concept of the paper is to study the LMTD (logarithmic mean temperature difference), Heat transfer Coefficient and Effectiveness (ε) of combined heat exchanger using acetoacetate/water mixture as a function of a diverse mass flow rates. This paper deals with the investigational study on the three different heat exchangers like tube in tube, shell and tube and combined (tube in tube & shell and tube) heat exchanger with acetoacetate/water mixture mostly to check the elevation of convective heat transfer coefficient, LMTD, effectiveness, overall heat transfer coefficient. These conducting tests give a synopsis of, the investigational study of the forced convective heat transfer and flow characteristics of a 25% acetoacetate consisting of 75% water. Acetoacetate/water mixture flow in to a parallel, counter direction in the tube in tube, shell and tube heat exchanger and combined heat exchanger under laminar flow conditions. A maximum increase in the coefficient of convective heat transfer of 56.3% and an effectiveness of 49.6% is recorded. And also compare this investigation with CFD analysis. However, combined heat exchanger provides better heat transfer characteristics than parallel and counter flow tubular and shell and tube heat exchanger due to the multi-pass flow of Acetoacetate/water. The overall heat transfer coefficients, Reynolds number, logarithmic mean temperature difference, the effectiveness of the acetoacetate/water are also considered and the results are obtainable in tabular columns and figures.