  A new method of obtaining the interaction Hamiltonian of phonons at
superfluid helium-solid interface is proposed in the work. Equations of
hydrodynamic variables are obtained in terms of second quantization if helium
occupies a half-space. The contributions of all processes to the heat flux from
solid to superfluid helium are calculated based on the obtained Hamiltonian.
The angular distribution of phonons emitted by a solid is found in different
processes. It is shown that all the exit angles of superfuild helium phonons
are allowed. The obtained results are compared with experimental data and with
previous theoretical works.
