Samer SawalhaKTH Royal Institute of Technology | KTH · Department of Energy Technology (EGI)
Samer Sawalha
Professor (Associate)
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59
Publications
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1,268
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Introduction
Additional affiliations
June 2013 - present
June 2011 - June 2013
June 2008 - June 2011
Publications
Publications (59)
This study evaluates heat recovery from a refrigeration system in a supermarket where the heat is supplied both to the supermarket and to apartments in the same building. As the incentives of the supermarket and the property owner are not necessarily aligned, collaborative heat recovery requires an agreement beneficial for both parties. The objecti...
This paper investigates ellipsoid-shaped macro-encapsulated phase change material (PCM) on a component scale. The selected PCM is a paraffin-based commercial material, namely ATP60; differential scanning calorimetry and transient plane source method are used to measure ATP60’s thermo-physical properties. A 0.382 m³ latent heat thermal energy storag...
Integrating latent heat thermal energy storage (LHTES) units into building heating systems has been increasingly investigated as a heat load management technology. A conventional LHTES integration method for heat pump based heating systems is to connect the heat pump’s condenser for charging the LHTES unit. This integrating layout however usually l...
This paper investigates the opportunity of utilizing the spare heating capacity of CO2 refrigeration systems in supermarkets to produce heat to be sold to district heating network operators. A comprehensive description and assessment of two control strategies that could be implemented to enable the heat export function are presented. To maximise th...
Heat recovery from local resources is shown to be a promising solution to reduce the carbon footprint of district heating. Supermarkets equipped with a CO2 refrigeration system and a geothermal storage offer a larger heating capacity, compared to traditional solutions. While district heat could benefit from this higher heat recovery availability, s...
Latent heat thermal energy storage has been receiving increasing interests in residential heating applications. In this paper, a numerical heat transfer model was built with finite element method for a cylindrically encapsulated latent heat storage prototype and used for investigating its thermal performance optimization measures. The model was val...
This study illustrates the potential of high temperature heat pumps (HTHPs) integration into district heating network (DHN) through a twofold approach, using DHN as a heat sink and source. It is used as a heat sink of HTHP that uses waste heat from the supermarket’s refrigeration system as a heat source whereas it is used as a heat source to HTHP t...
Latent heat thermal energy storage (LHTES) has been receiving increasing attention from researchers and engineers. A practical LHTES installation requires a deep understanding of phase change material’s (PCM’s) thermal behavior under thermal property testing and realistic operating conditions. To enrich this understanding, an experimental study on...
An important step during a project of a heat pump system is choosing a more suitable refrigerant. This paper presents a comparative study among refrigerants for a small direct expansion solar assisted heat pump (DX-SAHP). The mathematical model used in this study is presented in detail and validated from an experimental setup. The R134a is the refe...
This paper investigates the integration of geothermal storage into state-of-the-art CO2 trans-critical booster systems. The objective is to evaluate the impact of this integration on energy efficiency. Three scenarios of integration are studied including stand-alone and integrated supermarket building systems.
The results show that for a stand-al...
The integration of latent heat thermal energy storage (LHTES) units with heating systems in buildings is regarded as a promising technology for heating load management; however, so far a limited number of experimental studies have been reported that focus on space heating applications on a representative scale. In this study, we develop and test a...
Energy use is one of the main indicators for the economic and social development of a country, reflecting directly in the quality of life of the population. The expansion of energy use together with the depletion of fossil resources and the poor efficiency of energy systems have led many countries in recent years to invest in renewable energy sourc...
Projektet ”Morgondagens energieffektiva livsmedelsbutik” avslutades i februari 2018. Det har letts av KTH och genomförts i samarbete med en grupp industripartner, och medfinansierats av Energimyndigheten inom ramen för Effsys EXPAND-program. Projektet har utforskat en ökning av effektiviteten hos standardkoldioxidkylsystem i livsmedelsbutiker genom...
Energy use is one of the main indicators for the economic and social development of a country, reflecting directly in the quality of life of the population. The expansion of energy use together with the depletion of fossil resources and the poor efficiency of energy systems have led many countries in recent years to invest in renewable energy sourc...
The aim of this paper is to study the benefits of integrating CO2 trans-critical booster refrigeration system with geothermal storage. The ground is used as a heat sink for sub-cooling during the summer period and as a heat source for extracting heat in the winter season. Using field measurements from medium size supermarkets in Sweden, proposed an...
Una reducción del consumo energético en los sistemas de refrigeración y calefacción en los supermercados puede suponer un sustancioso beneficio tanto económico como ambiental. Por este motivo, el objetivo de este trabajo es estudiar la reducción en el consumo energético en los supermercados, encontrando la configuración más adecuada a través de la...
This paper investigates the state-of-the art features of CO 2 trans-critical booster systems. The performance of various modified features have been compared to the standard CO 2 booster system. Subsequently, the performance of the defined state-of-the-art CO 2 system is compared to natural refrigerant-based cascade, HFC/HFO-based DX and indirect r...
This paper reviews the guidelines of how to instrument, measure, monitor and evaluate refrigeration systems in supermarkets. The guidelines principles are firstly illustrated for a simple, single stage, refrigeration system: measurements requirements are analysed and the methodology to estimate refrigeration quantities are defined. Estimation for r...
Using heat pump technology to provide Space Heating (SH) and to produce Domestic Hot Water (DHW) for residential buildings has been widely applied during past decades. In this study, two scenarios adopting large-capacity propane heat pumps are defined and evaluated. These two scenarios, which are named after Scenario A and Scenario B respectively,...
In the process of moving towards sustainable energy systems for future cities, the district heating system will have to be more dynamic and accessible to the different heating sources available in the society. A main potential heat source to be connected to the district heating network is the heat rejected from refrigeration systems in supermarket...
This paper investigates the integrated and state-of-the art features of CO2 trans-critical booster systems. The main objective is to identify the most promising solutions in terms of energy efficiency impacts.
First, the performance of modified features and integrated functions have been compared with the standard CO2 system and alternative heatin...
This paper investigates energy efficiency of an integrated CO2 trans-critical booster system installed in a supermarket in Sweden. The supermarket has applied several features to improve energy efficiency including space and tap water heating, air conditioning (AC), and parallel compression.
Using field measurements data, the system performance is...
This part of the study investigates the performance of HFC refrigeration systems for supermarkets and compares the performance with alternative CO2 trans-critical solutions. The investigated HFC system solutions are typical in supermarkets in Sweden. The analysis in this study is based on field measurements which were carried out in three supermark...
The use of natural refrigerants has become of increasing concern in recent years due to the high GWP and ODP of commonly used CFCs, HCFCs and HFCs. The use of hydrocarbons can be considered as potential long term solution in heat pump applications. Propane is highly flammable and potentially explosive, however; with proper safety measures in place...
This paper investigates key operating parameters of a supermarket in Sweden where heating and air conditioning are integrated into the CO2 trans-critical refrigeration system. The Supermarket has applied several features of a state-of-the-art system including space and tap water heating, air conditioning, and parallel compression. Using field measu...
This paper investigates the energy efficiency performance of an integrated CO2 trans-critical booster system providing refrigeration, heating and air conditioning demands of a small-medium size supermarket in Sweden. Using a computer model and input data from field measurements (data presented in part-I of this paper), the system loads and energy e...
Heat pump applications working with hydrocarbons as refrigerant have been under significant development along with the gradual phasing-out of conventional HFC systems. In this study, a large capacity air-water heat pump prototype using propane as refrigerant is tested to evaluate its heating performance under different operating conditions. The exp...
International Energy Agency (IEA) presenterade nyligen sin plan för energieffektiva byggnader där termisk energilagring lyfts som en av fyra nyckelkomponenter i byggnaders värme- och kylsystem. PCM-baserad (Phase Change Materials – fasändringsmaterial) termisk energilagring (PCM-TES) har några fördela jämfört sensibla lager: kompakta system (hög en...
This paper theoretically analyses a CO2 trans-critical booster system in which parallel compression, heat recovery and air conditioning are integrated. The performance of the system is studied in various running modes using flash gas by-pass (FGBP) or parallel compression (PC). These running modes include summer cases with/without air conditioning...
This study investigates the refrigeration performance of three CO2 trans-critical solutions based on field measurements. The measurements are carried out in five supermarkets in Sweden. Using the field measurements, low and medium temperature level cooling capacities and COP's are calculated for ten-minute intervals, filtered and averaged to monthl...
This paper reviews findings of main projects at the Royal Institute of Technology (KTH), Sweden on supermarket refrigeration and heat recovery systems. A main focus of the research has been on CO2 trans-critical booster system, as the emerging solution in the Swedish market, where its performance has been often compared with the conventional HFC so...
This paper theoretically investigates the performance of a CO2 trans-critical booster system using various configurations of internal heat exchangers (IHX). A reference case performance is compared with eight alternatives of using IHXs after the gas cooler and liquid receiver. Cooling COP, total COP and amount of heat recovery are the comparison cr...
This study investigates the heat reclaim of trans-critical CO2-booster refrigeration unit in a supermarket in Sweden. The aim is to compare the control strategy for heat recovery in real supermarket installation to the optimum control strategy.
The optimum control strategy based on theoretical analysis is explained. By analyzing field measurement o...
This research paper theoretically studies the performance and control strategies of a CO2 trans-critical booster system. A computer simulation with field measurement-based inputs is used to analyse the performance of the system. Energy usage/efficiency indicators including cooling-heating loads, electricity use and COPs are presented and discussed...
This project investigates the potentials, challenges and opportunities of using CO2 as refrigerant in the supermarket refrigeration and heat recovery systems. The focus is on CO2 trans-critical booster system, as the emerging state-of-the-art system in supermarket refrigeration field. The CO2 booster system performance is studied using computer mod...
The objective of this research is to evaluate the potential of thermal energy storage in supermarkets with CO2 refrigeration systems. Suitable energy storage techniques are investigated and the seasonal storage technology of boreholes is chosen to be the focus of the study. The calculations are done for four supermarket refrigeration systems with d...
The average energy usage of an ice rink is around 1000 MWh/year, of which approximately 70% goes to the refrigeration and heating systems. CO2 as refrigerant has favourable properties in this specific pplication due to its low-toxicity and high heat recovery potential. The use of CO2 refrigeration systems in the ice rink industry has potential to p...
This paper studies field measurements and performance analysis of eight supermarkets in Sweden amongwhich five supermarkets use CO2 and three use HFC as the refrigerant. The differences in system design arediscussed and detailed performance evaluation of one of the systems is presented. The performances of allthe supermarkets are compared and the r...
Using computer simulation modeling this study investigates the performance of a CO2 trans-critical system with heat recovery from the de-superheater. The influence of sub-cooling (or further cooling) in the condenser/gas cooler on system performance is investigated. Following the suggested control strategy in this study, the extra operating energy...
Using CO2 trans-critical system solutions in supermarket refrigeration is gaining interest with several installations already running in different European countries. Using a computer simulation model, this study investigates the performance of two main system solutions: centralized with accumulation tank at the medium temperature level and paralle...
The performance of CO2 refrigeration systems strongly depends on the operating conditions. The specific characteristics of low critical temperature and high operating pressure limit its applications and imply the implementation of different control strategies. This study compares the performance of different CO2 system solutions for supermarket ref...
This thesis theoretically and experimentally investigates different aspects of the application of CO2 in supermarket refrigeration. Theoretical analy-sis has been performed using computer simulation models developed to simulate CO2 indirect, NH3/CO2 cascade, CO2 trans-critical and direct expansion (DX) R404A systems. The models supported the select...
In this paper we investigate and evaluate the performance of an NH3/CO2 cascade system for
supermarket refrigeration application in a laboratory controlled environment. The system solution
under investigation replicates a medium size supermarket in Sweden. CO2 is used at the low and
medium temperature levels with several possibilities available for...
Carbon dioxide is now being considered as an alternative for synthetic refrigerants in supermarket refrigeration. One reason for this popularity is that CO2 possesses a good quality as a refrigerant from environmental and safety concerns. Furthermore, it is inexpensive and easily available from the atmosphere.
In this study, we investigate the influence of the pressure and temperature drops in the suction and return lines on the energy consumption of a supermarket refrigeration plant. We calculate the energy consumption of CO2 indirect systems with R404A, ammonia or propane as the primary refrigerant and compare it to conventional direct expansion (DX) s...
In this study we analyse some safety aspects related to the usage of CO2 in supermarket refrigeration. The concentration levels in the supermarket’s shopping area and machine room that result from different accident scenarios are calculated for a selected practical example. The ventilation requirements in the supermarket under normal conditions and...
The selection of an available natural alternative to replace harmful artificial refrigerants depends on the application, which defines the system boundaries and the operation range. In the last ten years, CO2 was introduced as a semi ideal refrigerant due to its environmentally friendly and good performance characteristics. In some applications the...
The development of a laboratory test rig of an NH3/CO2 cascade system is presented in this paper along with a theoretical model that simulates the performance of the system. The system solution under investigation replicates a medium size supermarket in Sweden, it is designed to fulfil the general requirements of the supermarket and operate within...