The first part of this work provides the expressions and procedure for evaluation of heat transfer in plate type solar collector with and without tube sheet. Applying this calculation procedure, a number of simulations of collector work are performed, varying at that time constructional parameters. Following this parameter analysis, different numerical models for CFD simulation of heat transfer in collectors with and without tubes are developed. These CFD simulations are performed by means of the computer code Fluent, firstly focusing on the geometry of previously tested collector with tubes welded to the absorber by laser. The simulations are performed at altered constructional and working parameters with aim of considering possibilities for further increase of collector efficiency. These analyses lead to the construction of the collector prototype without tubes, consisting of two chevron plates normally used in plate heat exchangers. The thermal-hydraulic performances tests of developed prototype with and without glazing are compared against the results available from the numerical simulations and with the test results on collectors with tubes. The thermography is employed to record a temperature distribution over the prototype absorber plate in order to calculate the local heat transfer coefficients on the fluid side. A separate part of this work is devoted to the CFD simulation of the flow through the complex geometry of plate heat exchanger channel for the chevron angles β = 28°, 60° and 65°. The values of the heat transfer coefficients calculated from the results of these simulations served as a boundary condition for previously mentioned simulations of the heat transfer in collectors. All results are validated through the comparison with the results from the visualisation and thermal-hydraulic tests done on the corresponding plate heat exchangers channels, as well as with the thermograms recorded during the collector performances tests. Following the results of performed analyses and measurements, the instructions for simpler and thermally more effective construction of developed collector prototype are suggested. Generally, the developed type of collector without tubes represents a direct contribution to the efforts involved in producing a cheap solar collector of high thermal performances, avoiding rather complex and expensive technology nowadays employed to attach tubes to absorber in thermally effective way. Developed mathematical and CFD models for estimating the heat transfer in solar collectors and in plate heat exchangers channels, enable optimization of relevant constructional parameters in order to produce more efficient, simpler and cheaper device, as well as they allow for reduction of number of tests needed in designing process.