In this paper, normal spray impact onto a rigid wall, leading to the formation of secondary spray, is considered. The mechanism of splash is explained by the bending instability of a rim bounding a free liquid sheet. The linear stability analysis of the rim is performed in the framework of the long-wave, quasi-one-dimensional approach. The rim instability is caused by the moment of forces associated with the inertia of the liquid entering the rim. Next, two components of the drop velocity and their diameter, as well as various flux density vectors (number, volume, mass fluxes) and tensors (momentum flux), are measured using a phase Doppler instrument. It is shown that the viscous length scale of drop impact can be used in describing the splash threshold, diameter of secondary droplets, and their velocity. Consequently, a closed semi-empirical model for the secondary spray has been proposed and validated using a numerical simulation of spray transport based on an Euler-Lagrange approach.

In order to improve energy efficiency, the Croatian government introduced an individual metering obligation for all district heat network users. The purpose of the research was to evaluate this policy measure regarding its effects on tenants’ behavior and energy savings, but also from the perspective of cost-effectiveness. The sample includes approximately 20% of all Croatian users of district heat energy. Energy savings related to the installation of heat cost allocators are calculated by comparing the specific heat energy consumption, corrected for the number of heating degree days, in periods before and after the installation of the heat cost allocators. The cost-effectiveness assessment is based on the concept of the net present value. The transition to individual metering in Croatia resulted in significant energy savings averaged from 20 to 35%. However, low heat energy prices in cities with a dominant share of heat energy consumption did not ensure a positive net present value of investment for all buildings.